What Should I Do (bullying???)?

ok well,theres this girl (we're both 13 and in 8th grade) that keeps talking crap to me.i never did a damn thing to her and shes flippn out on me.today at school,in music cl,she was calling me ugly and saying that i was a loner(i dont have alot of friends,but still!!!),she was yelling and stuff,and i said shutup leave me alone and f*ck you.its her and her friend that keeps on doing this.they wont stop,i told the princible and she didnt do anything at all.my mom and dad knows about this,and they say that i should just fight with her,but im really small and skinny,and ive never really fought anyone,i was a fighter when i was younger but i do want to fight them because theyre really bullying me and theyll keep doing it until i do something,what should i do?