When you really like somebody but she fancies somebody else how does one cope with the pain?

I tried ignoring her but she lives across the way from me and I see her almost everyday as the kitchen is communal and we practically cook at the same time. But even then it is almost impossible to avoid her because I can't help deliberately bumping into her - some times we have very long discussions together which I thoroughly enjoy but I'm at kidding myself if I think that she fancies me - the guy who lives a few doors from us has caught her heart even though he only sees her as a friend and it hurts whenever the three of us are together because in her eyes I suddenly become this non entity, or quite possibly, an annoying obstacle that gets in the way of them consumating a relationship together. I have never had a girlfriend before despite my age and this no doubt fans the agony and jealousy I feel when I see the two of them together. She craves his attention and I crave hers.When you really like somebody but she fancies somebody else how does one cope with the pain?
Based on your question's description you seem like you really have a way with words. Try writing or a poem or story--whichever appeals to you. That's always a good way to get your feelings out. And if that doesn't seem like your thing, talk to someone you trust and feel comfortable talking to. Good luck.