I know a lot of women want to change love relationships into friend relationships, but it is awfully hard. I think part of the reason they want to change something into friendship is that they feel guilty about causing their guy pain. Maybe some men are willing to take such a deal hoping that the woman will eventually come to like them in a romantic way.
It doesn’t work that way. Usually they aren’t interested in you romantically for some chemistry reason. You just don’t inspire those feelings they are looking for. If they ever do want you, they are most likely settling, since they are unable to find what they want.
I think it’s horribly unfair to ask a guy to be a friend. They hang out with the girl, constantly wanting, and not getting. It’s just torturous. Yet many men will suffer the torture because they can’t tear themselves away. The women—maybe they don’t get this. Could they possibly want to torture guys like this? I doubt it. They think the transition from love to friend is possible. I don’t know why. Maybe it’s different for them.
I agree with @Marina. I think you have to discipline yourself and let her go. That’s what she wants, and when you think about it, that’s what you want, too. Go. Suck up the pain and loss. It will go away, eventually. If you find someone new, it goes away especially quickly. Try to remember her rarely but fondly. Whatever you had was nice—a true sign that she liked you (if not that much). But a relationship wasn’t possible for whatever reasons there are. Probably neither of you know them all. It’s sad. Very sad. Crying sad. Such is life.