After you file

@Mike9241 -  he already stated that she didn't begin living with him until April, so she can't be a qualifying dependent in 2019.  

 

as was stated earlier in the thread, the issue of whether the father could claim her in 2019 is between him and the IRS.   

 

I really wonder if the bigger issue is the stimulus payment which is easily rectified on the 2020 tax return without involving the father