Most Helpful Girl
Most Helpful Guy
Hang in there and keep waiting but be wary... unrequited love (liking in this case) does build up and if after she breaks up, you make her an offer and she rejects, it can be tough. I say keep your expectations real, be friendly towards her.
My world view, being that most moral codes and the practice of having respect for others aren't necessary, I would tell you to be friends with her, be nice, and try your very best to put her off him. I don't think your chances are good but try your best. Just don't make her think you're a creep. subtlety is key.