What recourse do I have as the POA for my mother?

I asked a question back in February 2022. My Sister and her daughter took my mother out of the Memory Care Facility and took her to bank and had her withdraw $100,000.00 and open a new account with just my mother and my sister's daughter on the account. I filed an elder abuse claim. they did their investigation and reported back that they did not find any financial abuse. I have an attorney request bank records of the account from both my sister and her daughter. My sister said she had no joint accounts with My mother and her daughter said it was a survivorship account and therefore she had not obligation to provide the statements. So, now when my mother passes, that remaining money just goes to the other person on the account. Also, me as the executor of the will, cannot withhold that amount from my sister. This seems like elder abuse to me. Now i am hearing rumors, that when my sister did this withdrawal, she also took my mother to an attorney and had the will and the POA changed. This is in a small town and my sister is the only sibling that remains in the area, so she is taking advantage of the situation. I have been communicating with my attorney and trying to find a strategy to get the old will back, if it has indeed been changed, and to get the 100000 back into my mother's normal checking account. My mother has not been medically diagnosed as incompetent, and clearly has moments when everything is fine. Other times she is seeing little people outside the window stealing birdseed. I'm at wits end trying to figure out how to proceed.