As POA your sister is bound legally to act solely in your mom's best interest. Comingling funds by withdrawing funds from your mother's account and depositing into her own - I'm guessing that is against the rules, so I would ask an attorney about it. They can tell you what can be done about it.
My brother is POA for my father and often has to buy things with his own personal credit card and then replaces the money with my dad's at the end of the month, just makes things easier
I do the same thing with my parents, use my credit card for their stuff and write myself a check from their account for reimbursement, and keep very detailed records should anyone ever question.
Windyridge, I do the same thing and we are partners. I worked in real estate for 40 years, and I can tell you, documentation is the name of the game. I NEVER was sued. Believe me, it takes time to document everyday, but it is worth it. I was first writing everything out and found out it goes faster if I type it out in a document on line.
Just to clarify, if your sister is taking out "all" of the money and transferring it every month, there must be some income coming in on a monthly basis.
What does your sister say about this? What are her explanations? What are her responsibilities, and is she using these funds for your mother's care?
As the question stands ... ask her why she is doing that and what records is she keeping to demonstrate what the oney is being spent on as it MUST be spent in the interest of her mother.
If you arent satisfied with the answer speak to the legal eagles
Please just a little more and then we'll very likely have all kinds of help.
What does your sister say about this? What are her explanations? What are her responsibilities, and is she using these funds for your mother's care?
As others said, we really need more information.
If you arent satisfied with the answer speak to the legal eagles