How do I legally go after a woman that continues to swindle my mother-in-law?

My husband is in denial and completely unsure of how to rectify this situation. Her friends continually call me to tell me serious events of how this woman is using her credit cards, stealing items etc. She moved in took over conned her completely. She recent moved out but now works for her at her auction building. People who've worked for her for years are scared of this woman and deeply concerned for my mother's welfare. They've even told me she's stolen items while they're setting things up for a sale. Can we have her investigated by the police department? What do you suggest? My mother-in-law is now getting into her life savings because her account keeps being emptied! Her workers say their checks keep bouncing which has never happened in 40 plus years. She's continually overdrawn yet she buys nothing. She's 89 years old and still to runs her auction business. She was quite successful until this woman came into het life. HELP!