My 18 yr. old daughter didn't receive stimulus checks as she was a dependent on my 2019 taxes. If I file a seperate return for her, will she automatically receive those?

If she still CAN be claimed as a dependent on the 2020 tax return, she will not be eligible for a stimulus payment even if she is not claimed as a dependent.

if she CAN be claimed by you in 2020, even if you decide not to claim her, she is not eligible for the stimulus.  IF she CAN be claimed and has no income to report, there is no reason for her to file. 

if she is truly not a dependent, all she has to do is file the 2020 tax return and the stimulus money will show on line 30 (currently TT is not yet programmed for the 2nd stimulus)