As a specialist in Elder Law I see this all the time. A parent is their own worst enemy. No one has a magic solution but here are some ideas. We would be happy to discuss this further.
You could bring in a social worker to try to talk sense into your mother. You could petition the probate court for a guardian alleging she is not making reasoned and informed decisions for her own safety and welfare. You could call adult protective services and advise your mother is unable to take of herself. They will come out and do an investigation and if they find she is not able to take care of herself and will not let others help they would file for guardian. Then you could step up and be the savior; as in good cop and bad cop.
These are just a few suggestions. Check out my web site thecenterforelderlaw.com
Good luck.
Don Rosenberg