What rights does she have and what can I do to stop her from accessing his bank account and to get his ashes back?

My father gave his girlfriend durable power of attorney. Does that mean that she is financially entitled to his bank account, life insurance and retirement? I'm his only child and I'm the next of kin but she used the durable power of attorney to obtain his ashes and is keeping them from the family. She has already drained his checking account of a $5,000.