It sounds like you got in WAY over your head. My mom would have *never* bought a newborn horse for me at 9 with the expectation that I'd be training it.
Having never trained a horse before (and how much horse experience do you have otherwise?), you really need to get a trainer. I know they're expensive and can be difficult to find a decent one, but think about it: If you don't, you will probably make little headway on her by yourself, and instead of spending high school on a nice, calm horse, you'll just have this regret and an expensive pasture pet.
In the meantime, you need to stop treating her like an equal and start treating her like you are the herd boss. Someone posted an exercise on here that I really liked: Put her feed in the trough, but stay standing there in front of her, blocking her. If she tries to push you aside, yell and give her a smack. You can use a whip too if you want, which is safer, as you can stop her before she gets close, and keep her at a distance. Let her know that you are the herd boss (who eats first in wild horses) and that she can eat when you're ready to move. Obviously, get someone to stay outside with you, in case she goes bananas, and be ready to move if she decides to rear.
You cannot show fear with horses; they know when someone is afraid of them and will take advantage of it. You sound like you are scared of her, and that is only going to make her keep up her attitude.