My dad (90) is in the hospital. I want him to go for rehab in a skilled nursing facility and she wants him to bring him home with her and get rehab at home. Who has decision making authority? Does it depend on which one of us admitted him to the hospital?
On the other hand, the rehab environment can be very confusing for someone with dementia. If the plan is to bring him home after the rehab (that is, he is not going to be living in a care center) then this interruption in his environment is going to be a set back in his dementia. Expect it to take a few months to recover cognitively from the rehab experience.
I would personally lean toward the rehab, but I can see value in both points of view. Here is what I suggest. And I'm serious.
Decide by flipping a coin.
The whole legal process of guardianship to decide between two valid and supportable opinion seems way out of proportion to the need.
If you and your sister are both truly trying to act in Dad's best interest and if you can usually disagree without long-term drastic alienation, then work together to make decisions on a case-by-case basis. It is too bad Dad didn't assign a medical proxy, but he didn't. With good will the two of you can handle this.
The other aspect of rehab is that it can be a respite for someone living alone, especially if the facility is outstanding (as are a couple I've found). Meals are hot and freshly prepared, nursing and aide staff are available, lots of rest is available, and there's no responsibility to care for a house or apartment.
The bad part is that rooms are generally shared, and often the roommate is someone who has the tv on all day long. That can make the situation miserable.
There's another issue and that is how long your father has been in the hospital. Three days hospitalization (of admittance, not observation) is necessary before Medicare will pay for a rehab stay.
There is an option that addresses both of your concerns. Ask the treating physician if your father is ready for home care, or if in-facility rehab would be more beneficial. If your father's getting minor rehab in the hospital, ask the therapists the same question.
Your father can always get rehab in a facility and continue with home care after discharge - that's how we've worked it. The "heavy" rehab takes place in a facility; the follow-up lighter and less intensive rehab takes place at home.
The machines would be more interesting to use. Not saying therapy at home isn't good, but there is only so much a therapist can bring into a home. You want the patient to be interested in what he/she is doing.