Help! I think I lost my Best Friend?

I have been best friends with this girl for over 6 months and we always had feelings for each other and were almsot going to date. She is kinda always in a bad mood and either takes her attitude out on me or holds it in. On Wednesday, she gave me a really nasty attitude and from then on, I stopped trying to comfort her and gave up all hope of ever dating her. But now, we dont talk, hang out or anything, and I really want to still be ehr best friend. WHAT SHOULD I DO?