Have to agree with everyone about the treats. Until she knows the pecking order, no more treats. Get your hands on any book by Parelli or John Lyons (his is the method I use). They both teach about how to show a horse that you're the dominent one by using body language horses understand, not hitting. I have two mustangs which I got from the BLM and they are both sweet, gentle animals. I had some problems with the gelding in the beginning thinking he was the dominate one, but using John Lyons round pen training helped immensly. Both Lyons and Parelli have training videos that are very good. You might see if you can find a place to rent them (one of our local tack shops has training tapes you can rent), as they are very pricey. This way you could see whose method seems to fit your style/beliefs better and make a choice from there. Another person who is really good is Linda Tellington-Jones, but I think I would start with the other two first. Good luck; once trained, mustangs make wonderful horses.
Liz
Liz