To followup: based on the average GPA of Georgetown Law admits, Tiffany Trump would have had to make the UPenn Dean's List to have a competitive GPA. The list is public.

She never showed up on that list. Ergo, she did not have a competitive GPA. It's possible she may have had a good LSAT, but she would have needed a very high score to offset the low GPA.

As Georgetown Law appears to have been the most prestigious law school that would admit her, this suggests she was a "legacy" admit (meaning, admitted due to her parents or application sponsors rather than on her own merits).