She has vision problems, edema, brain shrinkage, dementia and speech pauses. She has fallen twice. I have alerted her children but they aren’t doing anything, enabling her to stay there. Dad can’t hear well and has light dementia. She left the gas on once, and can longer do chores as she says she forgets what day it is. She isn’t showering and stays in her clothes with food on it for days. I’m taking care of bills, taxes, home aides, and food. If they don’t have prepared food, they eat cookies and chips, she cannot drive, and dad does but doesn’t like to. I’m concerned she could fall and dad won’t hear or gas left on but her children are not addressing this nor do they respond very much to me. I don’t know what to do anymore, dad is not a reliable caretaker as he needs care himself and she has dug in her heels.
Her children will not respond and will not help. Ever. That is clear, and it is their right. We don't have to help our parents, and you're doing it, so they're off scot-free. Whee!
Do you have POA for your dad? If you don't, you should. He may, if his dementia is not too noticeable, still be able to grant POA. The lawyer you hire will assess that. You could then evict her, sell his house, and use the money to pay for 24/7 care in a facility for dad. He needs it. His dementia won't ever get better, and you might as well deal with it now before it gets so bad he burns down the house or wanders over to the next town looking for bunny rabbits or whatever takes his fancy at the moment. Yes, it does get that bad.
If you don't get POA, you can apply to be his guardian. That's a whole 'nother can of worms, though. But at least you're in charge at that point. When you're in charge, you prepare formal eviction for the woman, notify or have your lawyer notify her children, and demand that she's out by such-and-such a date. It may take a while, but at least she is gone. Dad may object. So what? He is in no condition to make his own decisions now. He probably shouldn't be driving.
If he continues to drive and has an accident, that might take care of the problem altogether. But you don't want that because they both might die in the process, taking out the family down the street as well. Then dad is charged with vehicular homicide, and you're dealing with that too.
Or, another idea is to call APS and report two vulnerable adults in danger so they'll send social workers to assess the situation. You tell them you can't be responsible for dad or the woman, and they must find a place for them. Then you let them handle it and stay out of it.
Your choice of choices isn't looking good. But even the worst choice is better than letting things go on as they are. Decision by indecision is what it is called. I think you DO know what to do. The question for you is, how long are you going to wait to do it?