I'm sorry your daughter seems to be going through so much!
I have a few suggestions for you. Check her blood sugar levels: what is her diet like? Is it high in protein or mostly sweets? She can have pretty bad sugar lows with a diet that is high in sugar.
Another suggestion is to go to an ENT and check her ears. Since it seems to happen a lot in the car, it might be that there is some fluid problem in her ear that is causing her to become dizzy to vomit.
The only other thing I can think of is thyroid. Have this checked. I have a relative who used to throw up like this and needed thyroid medication. Doctors for children with this condition were hard to find, so I hope you have luck if this is the case.