Tax Return question on N-400. A friend is filling N-400 but

she never filed income tax return. She married to a citizen but her hu*****and died several years ago. She has two children with him so they are on welfare and she has no other income besides cash aid and food stamps. I didn't know until she aske dme to help her fill out the form that she never filed the income tax return. Will it affect her citizenship application even though she didn't work at all but lved on welfare? thanks