If she does not otherwise have enough income to be required to file a return and she has owned and used the home she sold as her main home for a period aggregating at least two years out of the five years prior to the date of sale then she most likely will not be required to file a return.
See https://www.irs.gov/taxtopics/tc701
However, note that if she received (or does receive) a 1099-S for the sale, then she will have to file a return but should be able to exclude the entire $250,000 (note that she should normally not receive a 1099-S from the closing agent given the sales price).
