Hi, between me and 2 of my other siblings, we have been taking care of my father who has been bed bound since June 2016. My parents live out of state and two of my siblings are where my parents are (one lives there and the other moved there specifically to help take care care of our dad). My dad had throat cancer surgery and since then could not walk, has a peg tube and cannot swallow. My mother is "in control" and lets us all know that every chance she gets. My mother has been getting/having her own issues, with control, her health, mental state, etc. She always seems to want to defy us when we have suggestions that could benefit my dad. She always tells use that we don't need to know everything when it comes to her and dad. We have also always included her so she doesn't feel left out or jealous that we pay more attention to him. She still will not even open up to us about a living will, finances, etc. We are all still pretty much in the dark for the most part. We think our dad may eventually need to go to a long term care facility which would probably be better for him but our mother is making it impossible to try to arrange anything. I'm not sure if she just doesn't want to pay for it or if she just likes to be difficult. We all thought he was going to pass away last summer but he has been staying fairly stable and his mind is still sharp as a tack. We just don't know how to handle our mother, I know she needs to give up some control because it's affecting her health/mind but she just refuses to. I think my mom has early dementia/alzheimer's but she refuses to get any testing or consider that possibility. Everyone gets stressed out and irritated too often. We are all at a loss on the next step except to just keep taking care of my dad at home, but there has got to be a better solution.
I might consult with an Elder Law attorney who practices in their jurisdiction to find out what your legal options are. Your dad may be incapacitated enough that he needs a Guardian and it sounds like your mother may not qualify. I'd find out what evidence you need and how you may gain control over the matter.
Of course, you can wait around and see if you can convince her to change, hand you the information and authority, or just wait for a crisis....that's just not me. I wish you luck.