The first thing is you have to realize that the problem is hers, not yours. The only person in this situation that you can change and control is you. It's not what you want to hear, but you will have to accept her as she is and change how you interact with her.
You are not getting the emotional support you need / want from her and that is a crying shame. Your mom will never know what she is missing. If you keep trying the same things you will keep getting hurt.
I know you can't just run out and get new girlfriends, but you do have us. I promise I won't call all your relatives with every last detail.
Seriously, I have gone to therapy over similar issues and the only way I got to be at peace with the situation was to accept things as they were and change my reactions / interactions. I really needed the therapy more to deal with giving up on ever having the relationship I felt I should have had. It was almost like grieving a loss.
I don't know if any of this makes sense, but I hope what I'm trying to say gets out of the fog that has taken over my brain! I truly feel for you and understand what you are going through!
