Mixups are Millia’s greatest strength, so it’s natural that she has a lot of them. Most of her mixups will either be protected by an H Tandem Top, FB Pretty Maze, or Secret Garden, so if the mixup gets blocked she gets to dash back in and either continue pressure or attempt another mixup.

First off, let’s begin with her options when she doesn’t have a projectile(we’ll just generalize the discs and Secret Garden as these for now). This can happen when she gets a knockdown that sends the opponent very far away, not allowing her enough time to dash up and set something up, or when she gets an airthrow at a certain distance.

Her general good low options are:
2k is the low that gives her the most options on block, but if she’s close enough to the opponent while doing it she can be reversal thrown. If she does it outside of throw distance, she won’t be able to combo 2k into anything significant if it hits.
2s has less options on block, but it has better options if it hits(chain into 2h if she’s close, and if she’s a bit farther chain into 5h2d). The proration on 2s is also better so combos will do more damage.
214p is the most interesting of the 3 options, as it leads into an immediate knockdown if it hits, but on block a few different things can happen. If it was timed really meaty(as in, the spike was already out while the opponent was getting up), then the move is not safe on block at all at -13. But if wasn’t timed meaty then it is safe on block. Of course, if Millia has 25% meter she can FRC to make it safe and also combo off of the 214p if it hits. The main reason to go for 214p over the first 2 options are that it’s a way to bait wakeup throws, since she’s considered to be airborne during this move. In addition, Millia hops in the air a bit in the 214p animation so it gives the illusion that she’s doing an overhead like Tigerknee Bad Moon.

Her general good high options are:
-Tigerknee Bad Moon
6k is the overhead that has slower startup and is easier to react to, and it can be reversal thrown if Millia does it close enough, but it’s safe on block(frame advantage actually) so it has good options if opponent guards it.
TK Bad Moon on the other hand, is very difficult to react to, and yields an immediate knockdown if it hits. It also beats wakeup throw attempts if the Bad Moon was done early enough. The minus side is that TK Bad Moon is not safe on block at -15 on block, so most characters can counter with something if they guard it.

Other options are:
-safejump j.s
-Tigerknee j.236d or low airdash j.236d
-IAD or low airdash j.214s
-Secret Garden
The j.s should be done very meaty as a jumpin, so that if the opponent tries to do a wakeup uppercut, she will land in time to block it. And if the opponent decides to guard the j.s, Millia can either airdash cancel j.s into something or land and continue pressure off of the j.s blockstun.
5k is another good neutral option, as it’s Millia’s most versatile normal, having tons of options on block or hit, and it has 6 active frames so it’s very easy to time as a meaty.
6p is a normal that does not have many options on block, but it’s mainly used to beat the opponent trying to do something on wakeup. It should generally be done as a dashing 6p. If the opponent tries to reversal backdash, 6p will catch their backdash recovery and she can combo from there. 6p also staggers on a counterhit, so if opponent tries to mash something out on wakeup, they will get counterhit. Also, 6p has tons of active frames so it’s also very easy to time as a meaty.
j.236d is nice because it is persistent even if Millia is hit, so if the opponent tries to do something on wakeup they will usually end up getting hit. For the j.236d options, if they are done right they will make Millia cross up and the opponent will have to block in the other direction. If they get hit, Millia will not be able to combo off of it in normal situations but if the opponent’s back was close to the corner she can. Also, if the j.236d hits as a CH, then it will wallbounce and Millia will be able to combo.
For the j.214s options, Millia should aim to make the pin hit meaty, and hold back while doing this to check for reversal attempts. Once she has the respect of the opponent, she can start doing mixups off of the pin, like doing a low airdash j.s after the pin or just landing and going low instead.
And finally, she can simply do Secret Garden off a far knockdown to seal off parts of the screen.

Now, we move on to H Tandem Top. There are two general situations for when she sets up H Tandem Top.

Non-Meaty H Tandem Top

Most of the time when Millia sets up the disc it will be non-meaty. This is off of situations like comboing into 2d xx roll, comboing into 2d and then doing run up H Tandem Top, aircombo into j.214s 6h xx roll, aircombo ending in j.d, aircombo ending in j.d j.236p, corner 214p into dash up H Tandem Top, and airthrow into dash up H Tandem Top. She has many options off of non-meaty H Tandem Top. The basic idea of all of these is that if the attack actually hits, the opponent then is hit by the H Tandem Top, which sends the opponent flying and allows Millia to dash up and combo off of it.

Low options:

2k is the general low option that will be used the most, as if it hits she recovers fast enough to dash up and combo and if it’s blocked the opponent then blocks the H Tandem Top, and Millia gets to dash back in and continue pressure or attempt another mixup from the Tandem Top blockstun.
2s is another good low, and it doesn’t prorate as bad as 2k so combos from this will do more damage, but if opponent blocks it, she doesn’t recover anywhere near as fast though she can still continue pressure. If 2s hits, sometimes she won’t recover in time to dash up and combo, but 2s is jump cancellable, so she can just do an IAD off of 2s and do a combo from there(or even go into a mixup if 2s is blocked).
2d should generally only be done if the opponent is somewhat far away.
214p has the same use as described earlier, a low that baits wakeup throws. In the corner, if 214p hits with the disc set up, she can combo off of it but if it is midscreen she can’t combo off of it. To combo off of 214p midscreen she requires an FRC on it, and the FRC has an added effect of making 214p safe to reversals.

High options:
-Tigerknee Bad Moon
-214p whiff FRC j.k
-Instant j.k

Depending on how meaty the 6k was timed, it can be difficult to combo off of it if it hits midscreen.
For TK Bad Moon, it should be done immediately after setting the disc, and should be done as low as possible. If it is done correctly and the opponent fails to block it, they will get launched by the disc and Millia will be able to dash up and combo off of it. If not, then the opponent will just get hit and fall to the ground(which is still good, but not as good as comboing after).
214p whiff FRC j.k is quite possibly her most evil mixup ever, as it’s basically impossible to block on reaction considering she also has the low option of normal 214p. In order to make 214p FRC whiff, you either need to time the FRC perfectly so that you FRC on the 17th frame(very difficult, requires perfect just-frame timing) or you can do the much easier method of standing a bit away from the opponent and not be so close to them so that you can FRC on the 18th to 22nd frame, making the 214p whiff. If it is timed right, this is safe to reversals, as 214p whiff FRC j.k has the same effect as making a j.k hit very meaty, so she lands and is able to block in time if the opponent uppercuts.
Instant j.k is another option, but definitely the most difficult out of these 4 to use properly. The idea is to make instant j.k hit on the opponent’s reversal frame, meaning the 1st frame when they wake up. Every character in the game assumes their standing position for at least 1 frame after they wake up, even if the player is holding some other direction. So the opponent is in their tall standing position hitbox, but blocking low, so instant j.k hits. This also doubles as an anti wakeup jump maneuver, even if the instant j.k is mistimed, as if the opponent tries to jump on wakeup, they will be forced to airblock the j.k, followed by the 236h, which will drag them back to the ground. Millia can then descend with j.p/j.k, or land and continue pressure.

Other options:
-Tigerknee j.236k
-IAD over opponent’s body, j.236k/airdash back

214k is a crossup, and is also very good for baiting Dead Angle Attacks. However, if the opponent sees it fast enough, they can throw you out of it. In addition, it is also not safe against some uppercuts, as some uppercuts hit low enough to still connect during the roll.
TK j.236k is also a crossup, and it should be done very close to the opponent.
The IAD mixups are actually extremely easy to react to, and competent opponents will be able to block those on reaction most of the time. Therefore, they are only good to throw out only once in a while, when you think your opponent is getting used to your normal mixups. The IAD mixups also serve a purpose of baiting reversals, as if the opponent does a reversal their controls will get switched since you cross them up with the IAD.
In addition, all of the neutral option mixups that were described in the non Tandem top protected section also apply here.
For the throw option, this should only be done if the H Tandem Top was delayed a bit. So for example, doing j.214s land 6h xx roll 236h in corner, the 236h should be delayed instead of doing it immediately after the roll. The reason for this is because the GG system makes it so that there’s 8 frames of throw protection when someone wakes up.

Meaty H Tandem Top

These are more situational than non-meaty H Tandem Top, as the opportunities to set this up are way more rare than the former. The general way to set up a meaty Tandem Top is to do a very close(generally with dash momentum) combo into 2d xx 236h, or do an aircombo ending in j.214s land 6h xx 236h. Both of these require the corner. For the aircombo, you need to be extremely close to the corner when doing the 6h. In addition, the combo counter has to be relatively low, so no rejump combos please. If not, then the H Tandem Top will be out of range when the opponent wakes up and they will be able to escape for free. The benefits of doing a meaty H Tandem Top setup are that the opponent cannot reversal backdash or wakeup jump out of it, and many of the mixups that arise from meaty H Tandem are reversal safe. However, the mixups themselves are more limited than the ones for non-meaty Tandem. Generally, all of the mixups from meaty H Tandem start with an IAD.

Low options:
-IAD land 2s2h aircombo
-IAD land 214p

These are pretty self explanatory. It’s a meaty disc so the disc won’t hit after 2s hits, so 2s needs to go directly into 2h for a combo. 214p gives the illusion that she’s jumping for TK Bad Moon.

High options:
-IAD late doubleairdash j.s
-IAD land 6k
-IAD land Tigerknee Bad Moon

These are also pretty self explanatory. For the first mixup, after the j.s connects, Millia has a variety of options. She can link into 5s xx 236s and go into an aircombo from there, or she can link into 5s5h xx 236236s for more damage, or she can just do link into 5s5h2d for a knockdown.
For the mixup with 6k, Millia cannot cancel 6k into S Tandem Top as she can’t put out another Tandem Top until 42 frames after the previous Tandem Top(in this case, the H one) has disappeared. So instead, after 6k Millia should either do 6k xx 214p, 6k xx 214s214d, or 6k 5s xx 236s. The 5s link after 6k is pretty tough and requires some practice.
The 3rd mixup with TK Bad Moon is self explanatory, but since the disc is meaty, it won’t launch opponent after the Bad Moon hits, so Millia will either need to FRC or RC the Bad Moon to further combo off of this.

Other options:
-IAD j.s

j.s hits high, but let’s face it, no one is ever going to get hit by an IAD j.s as an overhead unless they were trying to do something on wakeup and failed the reversal timing. The idea is that the opponent will block j.s, and after that Millia has numerous options. After j.s, she can airdash cancel it into something else like j.ks, or airdash cancel into an empty airdash and land and throw the opponent. Or Millia can just land and just work off of the blockstun of j.s for added pressure.

In addition, all of these mixups can be done with a simple forward jump, but I find that doing an IAD makes them harder to react to.

Forcebreak Pretty Maze

These are generally set up the same way as non-meaty H Tandem Top setups, but they cover the weaknesses of them in the sense that wakeup jump and reversal backdash are nowhere near as effective against FB Pretty Maze(since Pretty Maze has 43f startup as opposed to 60f startup for H Tandem Top). They also cover reversals, as if the opponent reversals and hits Millia, the disc won’t disappear and in most cases the opponent will still be hit by the disc afterwards, resetting the situation. With the exception of throw, j.s, and airdash j.214s, all of the mixups described in the non-meaty H Tandem Top section also apply here. In addition, she gains a few more mixups.

High options:
-Fuzzy j.k

Instant j.k becomes a dangerous fuzzy overhead in this situation because of the multiple hits of FB Pretty Maze. In order for instant j.k to hit as a fuzzy, the opponent needs to block high and then switch to low block very fast. If they’re doing this normally as they wakeup, then instant j.k will hit as an overhead and Millia can combo afterwards. However, most of the time she will need to trick the opponent into doing this. You can induce the opponent to block high and then low in a variety of ways, but in this situation usually you will have to do something like jump over the opponent or cross them up with 214k or tk j.236k and then do instant j.k. The whole reason instant j.k can hit overhead(other than opponent’s reversal frame) is due to fuzzy guard. The meaning of fuzzy guard changes depending on context, and I think it’s called ahoge chuudan in Japanese which would clear up any inconsistencies. The whole idea is that the opponent will get hit(in their bigger standing hitbox) while they are crouch blocking. You can go look up the meaning of this in other places, I don’t really want to explain it here. Making instant j.k work as a fuzzy depends a lot on how the opponent behaves, so it is up to you to figure out their guarding tendencies.

Other options:
-214p FRC j.k

I can’t even categorize this as a low/high/neutral option because a low followed by a high. What distinguishes this from the earlier 214p whiff FRC j.k mixup is that the 214p in this situation doesn’t whiff and actually touches the opponent(hit or blocked, doesn’t matter). If either of them hit, then the opponent is juggled by the FB Pretty Maze and Millia can combo off of it as she pleases. Awesome!

Secret Garden

These setups are always done in the corner, off of either aircombo into j.214s land 6h xx Secret Garden, or ground combo into 2d xx Secret Garden. Millia should take care not to do Secret Garden setups if she’s too close to the opponent, as if she is too close the opponent has enough time to throw her after they get up(Secret Garden has 56f startup and it still takes time for the orb to move so it is impossible to make the orb hit meaty). Also, there are certain characters that Millia should not do Secret Garden setups on. In particular, she should never do them against Chipp and Baiken. Chipp can escape for free every time by doing wakeup teleport, and Baiken still has to block, but she can guard cancel Ouren the instant the orb touches her to escape. And against Potemkin, Dizzy, and Slayer, she should make sure that she’s even farther than usual from the corner when doing Secret Garden setups from there. If she’s close enough Potemkin can just walk up and do Potemkin Buster, Dizzy can do her Necro’s Anger super, and Slayer can do Dead On Time to escape.

As for different Secret Garden orb formations, there is a wide variety of them. The one that I like the most is 1h6h4h6h, which makes the orb move diagonally backwards(in Millia’s direction), then move forwards, back, and forwards again. I find that this one covers the most space and is the easiest to do combos off of if Millia’s mixup is successful. In addition, I also find it the most safe, as if the opponent attempts to attack Millia the orb will interrupt them. Experiment more with Secret Garden orb formations and find what works for you.

All of the low and high options described earlier in the non-meaty and meaty H Tandem, and FB Pretty Maze setups also apply here. In addition, she gets another mixup in the form of:

High option:
-Fuzzy j.k

It’s the same idea behind the fuzzy instant j.k that was described earlier in the FB Pretty Maze setup section, but this time, since Secret Garden has much more active frames, she has more ways of inducing the opponent to block high then low quickly. Doing a jump or a crossup and then instant j.k still works, but this time Millia can also do a jumpin, like a very deep j.s, and then land and do instant j.k immediately from there. Most people have a tendency to block low immediately after they block a jumpin, so this is why this works.

And there you have it. Those are basically all of the basic and common mixups that Millia has. She has much more mixups than these, but those are generally more situational and require more meter. For more, I highly recommend watching all of the Millia combo videos that are out right now, as many of those videos contain extremely creative and ridiculous mixups.