How do i get her to stop pretending to hate me and like me?

so i'm like thirteen years old in 6th grade. There is a girl in my homeroom and in some of my cles that i have known for like 7 years. i have a crush n her and she "pretends" to hate me but when no one else is around seems to be nice and laughs with me and stuff like that. people say she likes me and she says she like a mystery someone. i am pretty darn sure she likes me back (I mean some on she alwas hits me and stuff and yet is nice when no one is around) but i don't know what to do know. any help?