Help with School, Bullies and Probloms?

Okay it's a long story short. There is this girl at my school who used to be popular and all the guys wanted her except there was one problem she was a Bi**c. She always had to be the best one, always prettier and sluttier so her group ganged up on her and kicked her out. Thats where I come in. I made good friends with her and after a while we become close but she kept making me feel bad about myself tellimg me I was fat. Making me look bad infront of friends and she HIT ME! I had a hige bruise in my FACE and on MY Arm from her hiting me, she was trying to tell me she had power when I did something she didn't want me to do. So then me being a strong person said that's it. I told her I didn't want to be friends with her because she mistreated me and she had an extreme bad reputation as a slut. Which than I also got because I hung around with her. She deleted me off Facebook, all of our photos etc. But SHE IS IN ALL OF MY CLASSES at school! She has three good friends in our class (All of them Boys, who are ugly and try to suck up to her) Everyday I get tormented from them pushed around, shoved and called extremely bad names like Cu*t etc. So thhe other day I was at a friends house and we had a party and I got drunk (I am the legal age) and I took photos imitating her and put them up on facebook! Of Course she saw them and I got a lot of hate comments :( Now at school its all going to get worse What am I gonna do if she goes to the principal. I cannot tell him I am being tormented because I will get blame for it too. :( Help (sorry this is soo long)