HELP!!!!!!!!!!!! HELP!!!!!!!!!!!!!!!! MIDDLE SCHOOL 911~!?

well best friend.. not so much anymore ok so me and my friend have been close seens about 6th grade not much to the story its just last year we were like "friend/enemeys" we would always be mean to each other and she used to say like "oh me and mandy have a special realenship we always fight but were like best friends" and we were in health and pe last year togather so i guess thats why it didnt get that bad, this year were not in any cles togather and the friend enemey thing has turned SERIOUS like i have no idea when shes messing around anymore! today shes like "go away mandy no one wants u here" then im like "oh my god shut the f up"! then shes like "gosh im just kidding!" and it gets SOO annoying because im actually ending up to hate her! i cant talk to her like a normal friend anymore and im so pised off right now tht i just wanna throw away our friendship and ignore the prob cause shes being such a bch but she hangs out wit my other friends so i ahve to deal with her all the time! she always things shes better then me like she always says "haha hi shorty" and like all tht stuff shes just annoying she acts like a slutt oo and says i have no dude what do i do?