Did your health insurance company pay for your medical expenses? If you answered, "yes," your health insurance has right to be reimbursed. You should speak with a personal injury attorney who could review your case and go over your options in details.
She can't appeal the USCIS's decision, if that is what you are asking because you will need to show documents that she was not out of the country for more than 6 months. In this instance, she was clearly out of the country for more than 6 months. When did your mother return? Depending on when she returned, she has to wait and can file according to what my colleagues have advised.