In my room crying hysterically-Please help me?

This girl said i stole her boyfriend, because i was friends with her for like 2 days and her and her boyfriend broke up so I started talking to him (with no intentions to date him) and eventually we started going out, and that was two weeks ago and the first week was completly horrible she said I ted him and I stole her boyfriend, which I didn't do either! They were already broken up, and she thinks i'm the reason he won't take her back(which i'm not, he said he was tired of her breaking his heart) so half the school thinks i'm a because of her, which i'm not! Tonight she had people prank call me saying i'm a f^^^ing slut, , i look like a guy, ect.. Really hurtful things. I told my mom my boyfriends ex was saying bad things, and she didn't think much of it.. I don't know what to do :( Its like all my friends have turned on me. people i thought were my friends went to her side. i have no idea what to do, i'll kill myself if it continues like this for another couple weeks... And I cant get into a fight with her, shes alot bigger than me..