How do I patch up this coworker friendship?

Help for a friend with a real bad work friendship issue. I have a friend who is trying to patch up a good friendship with a female coworker at his job. Apparently, they have been friends at work for about seven months. In the last month though, it all went steadily downhill. The female coworker revealed to him her living situation finally and also revealed she was gay or bi (with preference for women)..not certain, and was seeing someone. Two weeks later, he felt it was time to tell her honestly he had feelings for her and it upset her a bit. He made it clear he was ok, he was over it, and wanted to remain friends. Now, she wants to spend less and less time with him even talking just at work. He has discussed this with other coworkers that while they agree, this situation needs time to heal, they also feel this girl is acting really immature with the issue. But, the situation is real aggravating and my friend is looking for immediate solutions on how to patch things up eventually. Ignoring the issue or blowing is too difficult since they work often close by to each other. It would just end up making things more difficult. He has been a extraordinarily supportive friend to her whenever she had problems. I think he needs to be treated better by her regardless of she was /bi or straight, taken/not taken, or just not interested.. It is just not right to have things the way they are. What kinds of strategies can be made on how to help him patch things up with this girl? Serious replies only!! Thanks much!