So this is going to sound really cold since your mom just passed, but you need to file a police report for identity theft. The good thing is that she's beyond prosecution now. Then you contact the credit card companies with the police report in hand and tell them these accounts were opened fraudulently. You don't need to mention your mom as the perpetrator at all. Check your credit report too in case there are any other cards you're unaware of. You are not liable for fraudulent debt, but you need to report it to them as soon as possible.