I don’t remember much about this movie but it involves three bullies one girl and two guys tormenting this girl. Calling her fat and such.

She is also later raped by an older man. It’s a story on how she gets revenge on them and deals with her bullies.

It may be Scandanavian or German. It features a scene where the bullies drag her into  school bathroom and abude her and she dreams of stabbing them and suddenly a rat appears.

Here is a clip from the movie, only one I could find – http://sexscenemovies.net.prx2.unblocksit.es/prinuzhdenia/1297.html