Maybe this girl didn't have a lot of friends before. You should try to get to know her - maybe you two might have more in common than you think. Also, just because she's in the spotlight just now, doesn't mean that you're other two friends have forgotten you :) Hope I helped.
My friends and I used to be a three. Then this new girl came and I was elbowed into the background. These are my only friends (other than my virtual ones!). I can't get a word in edge ways because of this new girl, what should I do?
Confront her about the situation and tell her why she did those things. If she's being cooperative and giving you honest answers, you two can work things out.
However, if she isn't, that would be the perfect time to report her to somebody. She can't just physically abuse you like that and then continue to harass you when you're trying to figure out what's up with her.
If they were really your friends they would listen to you. I think that maybe it's better to leave them alone. This girl sounds like bad news.