We all live in other states my youngest sister moved out mother in with her. My sister doesn't talk to me because she tried to defraud me and a insurance company out of claim money with fraudulent estimates . Well it back fired and I got paid the money. It was my claim. Hit n run my car ruined front of her house swipoed no damage she turned in a 10,000 estimate for the house while my car was damaged and the insurance people paid me total loss . My sister wanted that money and other. Now she doesn't want to do or see or have anything to do with me or my my mom . She can't keep mother from me, my mom would t know if my sister is busy her son a car her husband. A car with who's money. My mother wouldn't know the difference. She stopped my mom from helping me said I was taking advantage she has control and mom can't give me money she won't allow it. My mother offered wanted to help I was going to pay it rite back . What to do. My sister is a fraud manipulating theiveing liar. She spent her husband's 35,ooo inheritance behind his back all of it . Wined at Christmas a time for gifts for her kids online to get free baskets and toys from charities then when and bought her kids Xbox. Niki shoes. Ect. But will never admit she does any wrong ever it's everyone else's she play the cover but her intention are all about her sorry I got off track delet this . See why I would like to be watching her
https://www.agingcare.com/questions/now-for-my-sister-to-be-her-poa-does-it-have-to-be-a-legal-document-signed-notorized-or-just-word-of-498486.htm
You don't have any "rights" but you can report the situation to APS and/or bring evidence of her financial exploitation of your Mom to an attorney and then realize you may not win and will still have to pay the attorney. But an attorney can write a letter to your sister demanding she show the PoA paperwork to the courts. If she doesn't do this then you may have some leverage to get your sister out of the picture.
If you report your Mom as a vulnerable adult to APS and no one is her PoA, then social services will put her case in for a legal guardian who will be a third party and not anyone from your family since they will sense the fighting over your Mom's money. In the end you won't have control or even insight into her financial and medical affairs. They will transition her into a facility and you can visit her but won't have any ability to touch her money or assets.
If you can prove and have support documentation that she is acting fraudulently then you have a case. See an attorney and present the evidence. They will assist you if there is a case.
If the POA is enacted, she is within her legal responsibilities to stop you from getting money as it is a gift that does not benefit your mother and if Mediciad LTC is needed will harm her as it is a non allowed expense.