This disscusion has been brought up many times and what I get out of all the past post is that as long as the HS coach doesn't coach them they can play together all summer without restriction, but the HS coach has 10 days of contact during the June 1 thru July 31 and after that the exception is if they qualify for a National event.
It is true that a HS coach can have no more then 4 girls from the same team from his HS team, and incoming freshman do not count. The girls must have played for him the previous season.