Well, you're probably not going to change her overnight and the question is, do you really want to be around this girl? If I were you, I think I would find someone else with a good personality. Not easy to change people when they act like that. You can try through niceness and care but I think it would be best to go separate ways till she grows up and acts human.
Yes you want find other friends. If she's bullying you too much than you need to report her to school officials..
There are ways!
1. you can just go talk to her...take out all of your anger and tells her straight into the eyes.
2. you can complain to a teacher which will completely cut her off.
3. go talk to her and know the reason why she's doing so!
I'm not a very " bad works" tolerator.....so I'd just first take the 3rd option then the 2nd!
She might like you. They say when a girl bullies a guy that means she likes him.