this girl keeps messing with me

everyday i go to school i scared cause she bully me. and i ask her “why u bully me”. but her answer is “you have no witnesses”. every single day she does this. shes even throwing paper balls at me right now. i never did anything to her. and when i look at her she gives me an evil sneer. everyday she always hits m shoulder in the hallway. i am sick and tired of her bully me. it feel like abuse every school day.