The DPOA died with your father. If your father left a bank account ??? with your mother as the beneficiary, she need to make a claim against the bank now. Your step sister had no business taking the money from the bank???, and is reportable to the District Attorney, if the facts are as you state them, for theft. Take care of this immediately and make a written demand on the bank?? All the above would apply if this was an insurance company and your mother was a beneficiary.