Hate to tell ya this, man, but in my experience 90% of all flirting is just teasing, and not an expression of desire. She's probably just seeing it as being a sort of joke between friends, and doesn't actually feel for you. Tough break, man, but that's how life works. Might I suggest experimenting with asexuality? That's what I did after I was turned down very, very loudly, and very, very rudely, in a public place, with many of my schoolmates there, for a third time, and I haven't gone back.