No. A dependent cannot have a dependent. You cannot claim your GF if she made more than $4200 in 2019. And if she made less than that, she would not be getting the $2000 child tax credit. In actuality the most (and possibly much less) she would get is about $250 of "additional child tax credit" and some earned income credit based on the amount she earned by working.
The child-related credits are affected in a big way by the amount of income earned from working. Use the EITC assistant to see how much EIC she could get if she claims her child:
https://ttlc.intuit.com/questions/1899157-what-are-the-qualifications-for-the-earned-income-credit-e...
https://www.irs.gov/credits-deductions/individuals/earned-income-tax-credit/use-the-eitc-assistant
And here is how the CTC is calculated:
Look at box 1 of your W-2. Subtract $2500 from that. Then take that number and multiply by 15%. That is your refundable amount --or "additional child tax credit" amount. If you did not earn at least $2500 you cannot get any child tax credit at all.
**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.**
