I’m hoping the power of attorney your mom completed a while back will suffice for your long haul, too. The realities and legalities make your situation a bit murky.
The answers you found in your research only hold true sometimes. The legal reality is that states have different laws controlling powers of attorney. Many of them now include reciprocity provisions—recognizing that a POA finalized in one state is also good within another state’s borders. But not all of them do. And some states simply have different picayune requirements for witnesses and such that are interpreted strictly so that a document in one state has no power in another.
Another truth is that when you move around and about and deal with different employees in different banks and other institutions, they may simply have different policies and different levels of knowledge about how POAs work that can make your life a living heck.
If your mom lacks the legal capacity to finalize a new POA or to set up accounts jointly, which could also ease your burden, then my advice would be to cross your fingers and hope for the best for now. It can help immeasurably if you are able to deal with the same employees in the same bank or other institution, who will simply come to understand your needs.
However, it sounds as if you may be contemplating a move—and in many locales, it’s not possible to appeal to the smarts and common sense of bureaucrats.
If you run into more difficulties in the future, your net and best move may be to have yourself or another responsible soul declared to be your mother guardian or conservator—responsible for dealing with her finances and other personal matters, You can begin to research the local legal requirements for this by searching for “probate court” plus the name of our current city or county.