Please help.... i feel absolutely friendless..?

I don't know what to do. I always take more time than usual to make friends but once i've made them i find them really hard to let go of like that. There's this one friend who'slike, all i talk to right now but somehow she keeps hurting me. She treats me like i'm a total nothing to her, and when she needs me she's so sweet that i can't believe i ever thought she was mean. And once she's done, i'm back to square one, hurt. I'd like her tell it on her face but i'm scared ... what do i do..?