This girl gets on my nerves?

Ok so this girl sarah is such a slut. She is in 6th grade and flirts with this 8th grader on the bus all the time. He doesnt like her and hes told her that. She HAD a boyfriend untill i told him about this. He dumped her. Anyways she like takes her shirt off on the bus and has a low cut cami on underneeth that shows half her bra. And she keeps talking to me and i HATE her. How do i get her to know i hate her???! I dont wanna be too mean but i dont wanna be nuce either. Oh and shes emo too.