I think just because she isn't interested in one like the other, it shouldn't mean letting her go. Why not let the relationship follow its own path and see where it goes? She could end up changing her mind. He could too. I feel like it should be open on both sides rather than just bringing in a 3rd for you both. I know people have their ideals [your ideal is the same as mine], but you should both be open to the idea that it could go different ways.
[Insert witty comment here]
Feel free to add me up on facebook
. - Just click here.
Do send a message in your request saying who you are and that you're from this forum. It will help me filter out any spam requests.