How do you go about updating a POA document from another state?

It’s up to the attorney or notary to decide if mom is legally competent to sign a new POA or any contract.

Short-term memory loss isn’t necessarily incompetent to sign. The important thing is whether mom understands the document she’s signing, not whether she ate eggs for breakfast.

As this POA cannot be updated in ANY state with the principal now having inability to change it you will have to use the document as it was assigned. That is to say you are now the POA for your Mom and will serve as such. If you pass the successor takes over. At the time of death of the successor the Niece can apply to be conservator or guardian if need to, and this would be, if she is next of kin, fairly easily done with the proof she is next in line to serve, with the records of those who served before her, and etc.

You might ALSO first ascertain that your Mom is for sure incapable of doing this. Short term memory aside, if you call an attorney to your home, and describe the circumstances he can talk with your Mom, she can make her mark to an added amendment appointing Niece as a third, and he can notarize it right there. This will NOT be without cost. So I would go with plan A. The niece is informed and willing to apply as conservator should this unusual circumstance come to be.

Best of luck.

Funky is correct. The assigment has to be made by Mom. If she has Dementia, she can no longer make a contract.

You cannot change or alter your moms POA's in any way shape or form. They are legal documents and only she can make the changes. And the fact that she has some mental decline and perhaps even dementia, she will no longer be able to do so as one has to be fully mentally competent to change a legal document.