I'm not telling you that you have not to feel guilty, because you already know it, do you?
Well, this is a nasty situation, when you 'd like to help somebody who doesn't want to be helped.
You should understand why your mother is so reluctant to get medical care, and address that problem. As a last resort, however painful, you may try to put the blame on her: "I can't get a normal life because you don't get cured".
Most of all you may need an expert's opinion, I mean a psychologist.

Just trying to throw ideas in...