Does the old POA need to be informed? She is not responding to phone calls texts or letters. We need personal information Social Security card does her husband have a pension did she have a pension this is just some of the information that the nursing home needs to process her in. Which is quicker guardianship or power of attorney we need things done ASAP
The principal must be competent to give her POA to another. There are POAs for finance and medical decisions. They can be separate or both covered in the same document. A Durable POA is one where should the principal become incompetent the document will suffice to make decisions without the principals consent. However usually two drs have to write a letter stating that the principal is incompetent.
You mention guardianship. This is usually necessary when the patient is already incompetent and can't make decisions. That is where a judge becomes involved. You can ask for an emergency guardianship which is what you might need now. Seek the help of a qualified elder attorney. It sounds like you will need one. You don't need a social security number to get a POA.
And no, the current POA doesn't have to relinquish her POA status in order for another to be appointed. The new POA document would need to revoke any other POAs previously appointed should the principal be able to appoint a new one.
I do not believe you can just decide to revoke the current POA's position unless you have very valid reasons (with proof) that this person is A) Neglecting their responsibilities (financial or medical) to the parent/s who named your sister as POA. B) Abuse of parent/s either physically, mentally or financially, again, you must produce proof.
Next question. Are they mentally competent to say they would like to legally amend the current POA over to you? If not, you cannot speak or change that for them without the consent of the current POA, or you can prove negligence or abuse of position regarding said parent/s. You cannot simply attempt to override this just because you don't agree with how she is handling things or sibling rivalry. If she is caring for the parent/s, upholding her responsibilities and they are doing well, then she is doing her job. She is not accountable to you and your wishes.
I would try to find out who the attorney is who created the " Will or Trust" that drew up the legal documents with your parents wishes and directives naming the POA, there is usually a secondary or third listed to take over POA in case A) The person named wishes to revoke their position as POA or B) Something happens to the POA where they are no longer capable of fulfilling their responsibility due to chronic illness, physical inabilities, i.e; accident, or unforseen death. C) Neglecting imparitive, critical, time sensitive responsibilities. The attorney is the person to talk to for all the details of what your rights are, or aren't under the present circumstances. The laws also vary by state.
More questions.
Why is it she will not return any attempts of communication? Is this normal? Is there a rift or issue between you both? Who's pensions are we talking about, parents or sister and spouse? Who's Social Security cards? Has sister (POA) agreed to nursing home and if so, why is she not handling the paperwork? Many things that just aren't clear. Nursing home trying to get a hold of more financial resources to pay for care? Please get advisement again from attorney before handing personal info over to facility should you be unsure. The wrong decisions can be unforseen & detrimental. Sorry for the longwinded answer! Hope it helped but get the facts, starting with the attorney and the will/trust. Wishing you a positive outcome!