I'm so sorry. She doesn't want to be alone: hello, she has a daughter who obviously cares about her.

I can sympathize with her feeling a fear about looking ahead to the waning of years, but I don't see how pushing you aside helps her. What are the changes she wants to make? I don't know what to say except that maybe if she's going through something, giving her time and space to sort it out might help. You can't control what she chooses to do anyway. The challenge would be to be able to do that and not let it reflect on you. Can you create an emotional distance between your feelings for her and her current behavior?