If she is 65 or older, she is required to file if her income, not counting Social Security exceeds $11,850. If she files, she will not owe any taxes. If she doesn't she will get a letter from the IRS requiring either that she pay their estimate of taxes due or else file a return. During February-April, you could probably get it prepared for free at an AARP/TCE site (you could take her papers in to them if you have a power of attorney form). Maybe she won't get that letter until then.
