My husband's dad has Alzheimer’s. Husband's care decisions are starting to cause a problem between us. Any suggestions?

We live in Florida and he is upstate. His sister is the caregiver but she basically takes his money. She is in her 50’ s quit her job so the dad can take care of her. I make sure my husband goes up to help her out from time to time. I offered to have him come live with us but his sister did not want that and my husband did not either. I don’t get along with his sister she doesn’t like me for what ever reason and is very jealous. She has asked my husband for money to help take care of the father while he receives way more than enough for his expenses. I try to give advise but my husband will not talk to his sister about what’s going on with his dads money and if something happens to his dad what is she going to do. I try to deal with this but it’s driving me crazy. When he is with his dad he does not call only quick texts does not concern himself with our home but goes overboard cooking for his dad and sister. I can’t stay at his dads home because it’s like a hoarder home and I just can’t stay there that’s why I offer for him to come stay a while and they can switch back and forth. His dad is able to do most things on his own but my husband gives him a bath and treats him like a child. I don’t want to be insensitive because I would help if he allowed me too, but it’s starting to cause a problem between us two. And I know his sister is loving every minute of it.