my dad passed away and his long-time companion is acting weird.

She tried to steal money from my dad's bank account but had to return it to his estate. Over 10'000 dollars is u accounted for and she swears she don't know where it went. A home equity loan was established by phone and the money vanished and she was with my father for 27yrs and he did not need any money. she is stealing and doing some under-handed stuff but we can't seem to catch her. what kind of lawyer do we need to get to the bottom of this?