does the POA specify which doctor has to approve the admission? I'm sure that you can get her admitted via ER on a hold kind of basis and then the doctors will discuss but if a psychiatrist is recommending she stay IP then I doubt any doctor is going to deny that. It seemed like gero-psych stays were usually a little longer because they are careful to not over-medicate and there are so many sensitivities to contend with. I seem to remember 10-14 days being pretty normal with some longer and of course some shorter.

It really sounds like this is a step you need to take before something out of control happens. I'm sure it is hard but it is for her benefit.