My dad is 80 and health and mind are declining. How can I get him help with family members who emotionally abuse and neglect him?

Whose child is the granddaughter? How old is she? Where are her parents?

If you'll pardon me, I find it a little hard to understand exactly what she's done. Theft is not "emotional abuse." And then on the other hand: if your father is independent, how is she "neglecting" him? In what way did she make the house unsafe? I can't quite get a feel for whether the situation is not as bad as all that, or is very much worse and warrants police or APS intervention.

Good advice from AlvaDeer about him assigning Durable PoA to someone trustworthy and responsible. That grandbrat sounds like she may have an addiction issue, hence things being stolen. Maybe she needs to pass a pee test in order to stay? Honestly she sounds like nothing but trouble and an energy drain. If family meeting nets no good progress, consider eviction process (is legal and takes 30 days and she can be forcibly removed by cops) but only by whoever has legal authority to do so. Don't feel sorry for grandbrat if she "doesn't have someplace else to go". If she doesn't stay away get a restraining order. One of my sons was a wild child and I allowed him to sleep in his vehicle when it was -4ºF rather than have him in my house. It motivated him. Job #1 is to protect your dad and his resources for his care.

You say that "a granddaughter" has taken over the home and made it filthy and unsafe. I would say then that would mean this is the daughter of another of your siblings? Sounds like time for a sibling family conference now. Is your Dad back home or is he currently at the home of his dead mother? If he is home, then the responsible siblings will need to intervene in trying to get together to get some help to your Dad in pulling the house back together again. A sit down with the grandchild and whichever of your siblings is the PARENT of this grandchild is in order, and the circumstances under which she can be there explained. That is the moral expectations and the expectations of upkeep of the house. As long as your father is willing to enable this child in her bad overall behavior, and if your father is overall not in the throes of dementia it should be noted that this honestly is sadly is decision. I would sit down at dinner out with the responsible siblings and the father, and would ask that he assign POA to one of the more responsible of the siblings, so that he does not have direct power over his checkbook. This will help in future if she wants money, as he will be able to say "Oh, honey, I am so sorry, but I don't control my own purse-strings anymore. Talk to my sons about what you can do around here to help me for a few dollars extra. Let me know if I can help in your jobhunt". Your Dad is, as you already know, at great risk of being used by this manipulative child. Give him support, frequent visits and make it overall just a bit uncomfortable for her to be there. If anyone has the space to put dad in a hand built "tiny house" on their property perhaps he would agree to sell his home for having some cash for his end of life needs, before she gets it all. You pretty much know what you are up against here but a war of words and arguments and fights will only make your Dad more uncomfortable and make him feel more endangered, so include him, move out of her range, and do your discussing in private and with great love and support for your Dad. Wishing you good luck and hoping you will update us on anything you find that actually works, because things like this can help others on the forum as well.