Why is she acting like this? HELLLLLLLPP!!!!!!!!!!!!!!!!?

Ok, well theres this girl in my cl, and ive known her since like grd.1 and were in grd. 8 now, and we used to be rlly close, and were BFF's. Slowly, she started calling me less and less, and acting rlly bitchy towards me. We didn't have a fight or anything. I never called her either, and now we never even talk outside of school, and barley talk to eachother in school. Now, my x-friend is rlly weird. Like she'll be constantly chaning her best friend every year. Like last year i was her best friend, a few months ago it was my other friend, and her latest best friend was another girl. She gets super close with one girl, like calling eachother everday, and constantly hanging out ect. I thought we were tight to the end, but i guess she really wasn't a true friend. we stopped being so close becuzz of alot of reasons. First of all she got a boyfriend, online, and all they did was talk to eachother 24/7 on the phone. I had no prob. with this, but her bf always liked judged her friends. She would like show pics of her friends to him on webcam, and then he would be like o shes ugly or something. And when shes around guys, she always tries to get attention. She acts totally diff. around them, and tries to humiliate some of her friends in front of guys. She'll like hit them, or spit in their face and like laugh rlly loud. I find it sooo annoying. I have to admit shes rlly pretty, but she doesn't have to put her friends down to get attention. So after being treated like crap for awhile, i rlly didn't want to be her friend. So afer our friendship ended, i try to avoid her. She continued treating me badly even now. Randomly she'll go up to me during recess or something and spray juice in my hair, ruining it and getting it all sticky and gross. Or she'll "accidently" spill food on my new shirt. And she like rams me into lockers , RLLY hard. Everyone else treats it like a joke since its not only me who she does this to, but i dont find it funny at all, becuuz with other ppl she smiles and laughs, with me when she does it, she shoots me dirty looks, or yells out LOOK! . She kicks, me rlly hard, and i have giant bruises on my knees from her. I always avoid her, but shes always like comes up to me and does something. She stole my moms money, which i had in my pocket and i was supposed to give to my mom. I find her so ANNOYING and i feel like shes trying to like control me or something, and she knows the things she does bug me but its kinda hard not FREAK out about things like that. And if i dont freak out, she'll do it to me more becuuz she knows she can. Onetime she shoved her hand in my face, giving me a nose bleed. Everyone was sympathetic, but she just stands there all innocent and is like o, i didn't do that some other girl did! Everyone like believes her. No one like talks bad to her when she does stuff like that. but if someone else did that, everyone would think that person was a *****. I can't handle this anymore, shes driving me crazy! My other friends stick up for me, but their still friends with her, and if i stick up for miself shes like shutup, and she does w.e she did again. how can we go from BFFS, to enemys? I dont get it?