I asked my best friend out a few months after we graduated college and it was a crap show. We hung ouy every day just her and I and we went hiking, out to eat, played tennis, did almost everything just her and I, made a great team and had a lot in common. I ended up falling for her pretty hard. She turned me down and I tried so hard to convice her to be my girlfriend. It shot me right in the heart and I didn't understand it. She ended up dating a guy her friend wanted her to date a few weeks after that she didnt even know, not to mention I hated those people. I went through a year of mental anguish. I told her she was trash and said mean things which I regreted. I did appologize and told her that I hoped she was happy but that I never wanted to talk to or see her again. It really sucked, and I still think of her. but it was what I had to do. I have no clue how she is doing now. She said I cared too much, and now I don't care at all. That's what she gets.
After giving up on women and literally doing everything by myself for a few months, I found a wonderful girl who treats me amazingly. Our lives fit perfectly. Far better than that other girl. Not to mention she has a doctorate and makes a ton of money. She cares for me and appreciates me. The other girl was nearly a fathom of what I thought I wanted. But this new girl is the real deal.
Just let her go and forget about her. You will always have her in your head. But there is a girl who actually wants to make you feel good and who actually cares for you, who doesn't just use you for your intelligence. Let that girl live her life without you. Do things by yourself and get out of the house.
I know how you feel man and it is time to forget about being friends with girls and I hate to say it, but get them to put out as fast as you can. That is how women are. If you don't try anything romantic in the first month they will see you as a friend. Now go try your hardest to get laid and and forget about it.