A GF cannot be a qualifying dependent to file as HOH--since she is not related to you. If you cannot claim your daughter you do not have a dependent that qualifies you to file HOH. You can only get the $500 credit for other dependents if you can claim your GF. And we do not know if you can even claim your GF. GF cannot be claimed if she had more than $4700 of income--not counting Social Security.
**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.**
