It is not required to file the return of her income.
Money received from some specified relative (including son) shall not be taxable as per IT act.
SHE DOES NOT REQUIRED TO FILL RETURN IF INCOME BELOW LIMIT RS 1.9 LAKH IN A.Y 2011-12
If she invests the amount received from her son and gets income of more than 2.5 lakhs per annum (not including amount directly received from son), it will be taxable.