Unless she has more income than the usual retiree, the taxes owed is significantly lower for seniors this year. There is a new $6000 senior deduction this year, and a tax credit to refund some of the Social Security additional taxes for seniors with income outside of Social Security payments, but not exceeding certain limits.

The biggest issue is if she has an IRA or 401k and didn't take a RMD. That needs to be fixed relatively soon to avoid higher penalties.

You likely will need to pay closer attention to your mom's financial and administrative tasks in the future. My biggest surprise was when my mom was no longer able to balance her checkbook. Not that it's important to do that, but she felt she needed to, but was no longer able to make it balance.