Without our knowledge our niece managed to get my mother with dementia to sign her as power of attorney without letting her son's know?

Swiss, time to get Guardianship for your Mom, that will override any Power of Attorney.

We were not aware that anyone was power attorney until my brother went to the hospital to see my mother because she and was given medication which was warfarin blood thinner. She begins to show bleeding in her stool. They said to my brother we can't allow you in cause my niece requested it. That was when we found out she was Power of attorney. we were not contacted about this decision. My sister been in a wheelchair all her life and my mother allowed my niece to be paid to help her. My mother had got lost while driving to an appointment. We know she was taking money out of my mothers account for her drug use and other things. My mother has mentioned to me on many occasion she would go to the bank and place money in her purse and it would disappear. Thousands of dollars taken out of her account.

Certainly sounds fishy. How is your disabled sister involved? I think you need to consult an attorney who specializes in elder abuse and see what your options are. Please let us know what happens. Others here have experienced similar things. Elder financial abuse is not rare.

Swiss, sounds like your niece didn't use an elder law attorney to get a Power of Attorney, as an attorney wouldn't have allowed your Mother to sign if he/she thought she didn't understand the wording in the legal document.

Can you get a copy of this Power of Attorney? Check to see if it was prepared by an Attorney, and check to see if it was witnessed by at least two people [depending on your State] and who was the Notary.

Prior to the niece making this Power of Attorney, who was the POA for your Mother? Your brother? Usually if a new POA is made, an attorney would notify the attorney who had drawn up the prior POA.