Claiming a parent

2016 was the first year I supported my mother.  She lives with me and pay for more than half of her living expenses.  She gets social security and a small survivors pension that was my dads of $344 a month, $4128 a year.   I'm told the social security is not taxable and I'm told that the pension is not taxable, although she did get a W2 from the company.  I know the cut off for 2016 is $4050 to claim a parent, is this small pension that she gets, $4128, taxable so that I can't claim her.  There is a $78 difference.  Any thoughts or advice is appreciated.