I have a pending POA Abuse case in which I am Plaintiff. My lawyer can no longer work with me. The case goes to trial in one month. The case in NJ

You need to file a guardianship action in the county in whcih your mother lives.  You will need to get a Certified Elder Law Attorney to help you becuase this case will get complicated.  You also have to evaluate whether or not it makes financial sense to go after your sister.  If she has no assets to pay back the money she took, then you could be worse off than when you started due to attorney's fees.