If SS was the absolute only source of income in 2016, then no tax return need be filed, HOWEVER, the administrator of the estate must be thorough. For example, if "the estate" sold your mom's house, and it was sold at a gain, then "the estate" may be required to file a tax return, report it, and pay taxes on it. This is just one example I am providing you.
I do this because if the IRS would have any reason to question the handling of the estate (I don't see why they would), then if it's determined that taxes were due, the IRS can do what is called a "clawback" of distributed wealth from the heirs, back into the estate so that taxes due along with fines, penalties and late fees, can be collected from the estate.
If you have a good and knowledgeable estate attorney, they should be well aware of all this, and you should be able to hold them legally and financially liable and culpable if things come back to bite you in the future because the attorney didn't handle things right, or they didn't property advise the estate administrator.
