Is this person going to admit that she was told not to use the card but, even after being told that, continued to make charges? If not, you can expect the police to tell you that this is a 'civil matter' and the credit card company to hold you responsible for the debt. (Even if she admits that she made charges after you revoked your permission that could happen - you take a risk when you give somebody your credit card and tell them they can make charges.)