Probably one of the weaknesses of the relationship you had was that it was formed as a result of the traumatic experiences of your respective divorces. Perhaps once the pain subsided, this woman you are pining away for didn't feel the same connection you did.
It's just my impression, but it seems that as we get older, or are coming out of a divorce, we look immediately for someone that is potentially long-term/marriage material. We forget that each of us probably went through quite a few failed relationships prior to ever getting married. Not every one was meant to be. That could be the case with this one. I know it hurts you, but your ex-gf may just want different things than you.
I can't remember how long you were together, but I do like to point one thing out to sometimes help gain perspective. Think about old girlfriends that you've broken up with in the past. Do you think about them still? Do you even wonder if they are pining away for you? Do you even wonder if you ex-Wife pines away for you? If the answer is no, that could be the same way that your ex-gf feels. She may have moved on entirely. I'd suggest you let her go. Get yourself back out there when you are ready. Right now you are in a very needy place that wouldn't be attractive to her anyway.
You cannot be lonely if you like the person you're alone with. Dr. Wayne Dyer