Pleasee i need help its urgent!!?? im gonna be in so much trouble?

hello well my story is kind of long but i would really appreciate it if you could read it... then moving on.. i have a german exchange student we are both 16 and shes a girl and im a guy so shes been here over 3 months already and theres only 2 left before she goes back to germany.. so ppl have been talking so much **** about her in school.. calling her ugly and like idk how many insults... and then last night she asked me to tell her what people said! and i said no but she kept on swearing she wouldnt tell anyone and i told her everything with the names of the ppl who did it so now she keeps telling ppl and its getting me in trouble and the worse part is my brother hates her and talked so much sht and for something i cant explain i told her ( i know im an idiot) and now she says she will say if she has 2 but my brother will kill me if he finds out i told her!! im gonna get in so much trouble, i just had an argument with her a big fight and idk what to do! im lost she had sworn she wouldnt do anything to affect me and shes backstabbing me! please what can i do???? im desperate hereee