If her wages are low the SSDI will not be taxable. But if she need to file a return like to get back any federal withholding in W2 box 2 she will have to enter the SSDI SSA-1099.
Up to 85% of Social Security becomes taxable when all your other income plus 1/2 your social security, reaches:
Married Filing Jointly: $32,000
Single or head of household: $25,000
Married Filing Separately: 0
