You know she needs the care, so one way or another, you have to get the care to her that she needs. The ideal way for this to happen is for her son to do it. However, if he doesn't, then you should do it. I would give him the option, but tell him you're going to call the county if he doesn't act. It might piss him off, but so what? He can live without getting things his way better than his mom can live without assistance.
The Rev