Girls Trouble...meh?

Ok so Ive never asked a question on here before but here goes. I like this girl, and Ive liked her for months now. We are good mates and i see her as much as possible. Ive always thought/hoped she might like me. Sometimes it seems like she flirts with me and she often calls me for no reason and we talk for hours on the phone, but nothing ever comes of it. Ive sort of resigned myself to the thought that it may never happen. Well a few weeks ago she kissed my best friend. He said sorry and stuff but i pretended i wasnt bothered. Well antway last night we were all at this party and it seemed like one minute she is flirting wih me and then she is all over my best friend again, But i know he likes another girl so im not worried about him doing anthing. It just hurts because he is my best mate and it makes me wonder why im not good enough. Anyway i would just like to ask: What this all means? Should I tell her how i feel? and Is it worth still hoping after this girl? Thanks