None of those really apply, as I am the family head, didn't pay support for the child, and there is no spouse or common-law spouse in the household. Is it possible the software is considering her return as making the claim for this amount since her employer deducted taxes and she is filing a tax return?
Someone else in your household is making this claim (each household is allowed only one claim for this amount, even if there is more than one dependant in the household)