I started having petit mals at age 11. I didn't know what they were until I was in college. They're more annoying than anything, not painful. Everybody feels a little different when they have them, so I'm not sure anyone could give you an answer of what they feel like and have it match what your little girl is going through. The most we can do is tell you what our's are like, and hopefully something will ring a bell.
How you feel before one is called an 'aura', and like I said everyone's different. Body temp can change, and it affects your senses, so you can smell weird things, hear ringing or have things go silent, have problems with your vision (things have a red hue, or go blurry out of focus), and a number of other things, most very mild, but annoying nonetheless. Most common with mine are heart racing, getting really hot, and not being able to concentrate. Sometimes they'll happen a lot in one day, and people think there's something mentally wrong b/c I don't respond the right way to their questions or comments b/c my head kind of goes blank for a few seconds, and I miss an important part of what they're saying. That's where it's really annoying.
I have quite a few friends who take depakote for either seizures or bipolar, and it works really well for them. I tried it myself, but had a hard time with it, as far as it messing with my stomache. But that's a common problem for me. It's a really good one to try. I'd talk to your doc about side effects too. I can only imagine how scary it is to watch your daughter go through this, but it sounds like you're an incredible mom. Hang in there.
"For I know the plans I have for you", says the Lord. "Plans to prosper you and not to harm you. Plans to give you Hope & a Future."