My Dad had a friend on his checking account and she cleaned it out when he died within days. Any advice?

My father died and had a friend on his checking account he thought they could get money for him in case of emergency. I went to the bank and they said she was a co owner when i talked to her she said she took the money out and if he wanted me to have he would have given it to me. Well he did in a will and i have been to probate now she said she needs the money to live on because she only gets ss of 850.00 she wasn't a girlfriend and rarely came around.