One state will honor another state's laws(with a few exceptions).
Your POA should be fine in multiple states.
The answer given does not imply that an attorney-client relationship has been established and your best course of action is to have legal representation in this matter.
Most states will honor another State's POA with certain exceptions. For example, while North Carolina does not require that the principal's signature be witnessed by two independent individuals (i.e., not family or relatives), but only notarized. You have not mentioned the other two states. I would suggest you add the witnesses as well as the Notary so as to be valid in the other States. But just to make sure, I would contact an attorney in each State and ask them what method works there.
**NOTICE*** The preceding was for general information and educational purposes only and does not create an attorney-client relationship. For legal advice, you should consult with an attorney of your choice. Licensed only in North Carolina
A person can have more than one active Power of Attorney at the same time, just ensure that they do not include language revoking earlier Powers of Attorney, which is often standard.
The law governing Powers of Attorney varies from state to state. Banks and other businesses in state B *might* honor a Power of Attorney from state A, but I suggest that you consult with an attorney licensed in state B to ensure that it will work. You might find an attorney licensed in both states that could draft one document that would be valid in both states.
Your mother can only sign such a document while she has capacity, so do this right the first time. If you cut corners now and end up needing for your mother to sign another POA down the road, her illness might have progressed to the point that she won't be able to.
Good luck to you!
My response does not give rise to an attorney-client relationship, is based on the facts given, and is offered as friendly advice and not legal advice. If you want to establish an attorney-client relationship and receive legal advice, then you should hire an attorney with whom you feel comfortable working and who regularly practices in the legal area where you need help to review the comprehensive facts of your situation.