What should i do about this girl?

ok, theres this girl in my school who i had a crush on for a long time. Last year i started to talk to her, and we became best friends. I've told her i liked her, and she told me that she liked me too. But she was moving and didn't want to start something with me, just to end up with a heart break at the end. Well we've been through alot, and always stood by each other. When i last asked her to be my gf, she said that i deserved someone better then her (i started to think that she nvr did like me). But she keeps on getting into these bad relationships with these other guys, who always break her heart. I want the best for her but i don't know what to do. I'm still crazy 'bout her, when i see her i always loose my breath,and i will get man nervous around her. But now we dont talk as much as we used to, were still friends though. What should i do?