Tax related to family pension received by a widow

Dear sir/ma'am, My mother is working with NC Rly Jhansi division. She had been given this job in 2012 on compassionate ground after the sudden demise of my father in the year 2010, who was on service then. My mother is getting family pension of my father along with her salary, now the question is that, will she have to file tax as per combined incomes from these two or she would be entitled to get exemption on family pension as per section 56 of the Income Tax act. Kindly help me out regarding this. Regards, Sharen Pradhan