High level player to me is defined as most girls on the top 3/4 of DA teams in SoCal that get significant playing time. And yes girls have already quit. Some probably largely due to parental expectations that they needed to play DA when their dd was not cut out for DA due to social life or school commitments. This is above the normal attrition you see at the start of high school.
So these "high level" players quit soccer entirely because of GDA? I don't believe that for a second.