If your GF's child lived with you the whole year and you paid for over half her support you may be able to claim the child as a qualified relative dependent and get the $500 credit for other dependents for her. Since she is not your own qualified dependent child you cannot get child tax credit, earned income credit, child care credit or use her as the dependent to file as Head of Household.
CREDIT FOR OTHER DEPENDENTS
https://ttlc.intuit.com/questions/4499708-what-is-the-500-credit-for-other-dependents-family-tax-cre...
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
