Grace is a blonde elf with magical powers swirling around her as flower blossoms. She often acts like a diva, but in private she is a nerd who spends a lot of time at her computer. Yes, she is basically a nerd/weeb/magical girl parody. So in terms of voice, Something like Sailor Moon would work, a bit high and cute but not too much. Since these are basically combat/ boastful lines anyway being able to give the voice some intensity and edge are required, see the sound clip (Grace-Slayers-Evolution)

Audition Lines:

Have a taste of my essence.
The Shining City would be dirtied by your presence.
Y'know what I hate? Cat ears.
Death is the end. But you can be remembered forever... if you're hot.

Ha! Ra! Hoo! (Fighting sounds)
Ahhh (Death/hurt)