Here is a collection of Millia’s voiceclips from the various games that she’s been in and the many pieces of music that have been associated with her throughout the series.

Millia GG Sounds
Millia’s voice samples start off pretty rough in the first Guilty Gear game, and she sounds very stoic.

Millia GGX Sounds
Millia’s GGX voice set is really hot, and also my personal favorite. Her voice becomes much softer and many of the samples sound like she’s whispering in your ear seductively. Unfortunately, it results in her being very hard to hear in-game, with the music drowning her out. I’m guessing the reason Sumitomo changed the delivery of her lines so much was that Millia’s outfit in GGX was a bit more revealing than her original GG outfit.

Millia GGXX Sounds
These are her voice sets used from Guilty Gear XX to Guilty Gear XX Slash. The sultry delivery of her lines gets toned down a bit, but it’s still pretty hot. This is definitely the voice set that most matches the way she talks in the Guilty Gear Drama CDs.

Millia GGXXAC Sounds
This is her voice set used for Guilty Gear XX Accent Core. She gains some new voiceclips for Emerald Rain and Silent Force. Her voice quality is reverted back to the way it was for the first GG: very stoic.

There is also a Youtube video that has all of her voices minus the original GG ones in it here:

Millia’s always had great music tracks throughout the series. Her signature track “Writhe In Pain” went through a lot of developments over the games and the GGXX version of it is the best version yet. Still In The Dark, her VS Zato theme in GGX, is a fan favorite and is one of the best GG tracks in general. The theme for Millia in the Korean version of #Reload, “The Great Empress” is also an awesome song and one of the best tracks on the OST.

Guilty Gear
Writhe In Pain (Millia’s Theme)
Way (May, Millia, and Kliff’s Staff Roll)
Brush Up (Millia’s Ending)

Guilty Gear X
Writhe In Pain (Millia’s Theme)
Still In The Dark (Zato-1 Vs Millia Theme)

Guilty Gear X Heavy Rock Tracks (also soundtrack for Dreamcast version of the game)
Writhe In Pain (Millia’s Theme)
Still In The Dark (Zato-1 Vs Millia Theme)

Guilty Gear XX
Writhe In Pain (Millia’s Theme)
Existence (Assassin Theme)

Guilty Gear XX #Reload Korean Version
The Great Empress (Millia’s Theme)
Red Crossroads (Zato-1 Vs Millia Theme)
Rogue Hunters (Assassin Theme)

Guilty Gear XX Isuka
The Irony Of Chaste (Millia and Venom stage theme)