My dad opened a llc in my mom's name,now they are suing her,however it was not my mom's signature.What's next?

When my parent's were married, my dad opened lots of credit cards and businesses in my mom's name. However, with this one her signature is forged and she did not know about it. They are now suing my mom for unpaid sales taxes on the business. When my mom found out about the business almost a year ago, she closed it as it was not hers. What will happen next??