The rules for a qualifying child are below. With the tax law changes in 2018, the answer is not so clear about forgoing the dependency. The rule used to read, that if the parent did not claim they exemption to be nice and allow their dependent to file as independent, the child could not take the exemption for themselves. Now that there is not more exemption, it is not so clear cut.
The bottom line is, if she is a qualifying child, she is your dependent. She would be excluded if she paid more than half of her own support.
Qualifying Child
Relationship — the taxpayer’s child or
stepchild (whether by blood or adoption), foster child, sibling or
step-sibling, or a descendant of one of these.
Residence — has the same principal residence as
the taxpayer for more than half the tax year. Exceptions apply, in certain
cases, for children of divorced or separated parents, kidnapped children,
temporary absences, and for children who were born or died during the year.
Age — must be under the age of 19 at the end of
the tax year, or under the age of 24 if a full-time student for at least five
months of the year, or be permanently and totally disabled at any time during
the year.
Support — did not provide more than one-half of
his/her own support for the year
