A friend got involved with a girl I like, what now?

Basically there's this girl I've liked for a while and she went single a few months ago, she's going to college with me in September and she thinks we're gonna be best friends, so do I. Anyway I was slowly gonna try and build something up with her and be more than friends but last week on a night out one of my friends kissed her and is now seeing her, nothing serious yet. He goes away in September, so I thought of it as a fling that will end by then, no biggie. But then they went on a date today and it stung me pretty bad, more than I thought. Will this ruin my chances of getting involved with her at college? I don't know what to do, I'm happy for him but I like her too. I'm gonna lose some weight in time for college and be the best I can be. But what does one do in this kind of situation?