I don't think anyone yet has offered a solution that I've seen, which is what the person wanted.
How about going up to her, taking the initiative. It can be hard, if you're not that type, but if you just go up to her and start talking about a problem that you need help with, she might get to see that others have problems, too.
She might have gotten so involved in her own problems and life that she's failed to see others' - but when she starts to see others, and what they need, then her life will not be as big a topic.
This, to me, is the bigger problem than her just talking all the time. That's a symptom, I think. But, there's a bigger pproblem, and that is she doesn't know anything else to discuss.
Elderly people often do this (sorry for the further generalization, but at least I didn't say always) because they don't have other subjects to discuss. But, I have found in talking with elderly people, if you tell them about your friends, family, life, etc. they will become interested in you and ask about you and won't be so concerned with their own aches, pains, etc.; they will have something else to think about.