I understand how hard it is losing a friend, it also happened to me a few years ago now. I strongly believe that before you can start to deal with anything else you need to start with you. Once you have sorted yourself out, got back on track and have a clear, clean head, then you can start to think about what to do next. I agree with what was said above that once he breaks up with her, she will come back to you. Don't think that she has just forgotten you because no matter what you will always be in her heart.
I hope all the advice given to you helps and your problem gets sorted soon
xx