My daughter's team has been on the end of blowouts like that. They played up in a tournament against a 6th grade team last fall, and the opponents did the press/fast break thing all game long. Not pretty.
It can be hard to hold the score down sometimes. In my daughter's 2 tournament games yesterday, they won by a combined 106-11 (58-5 and 48-6). By local rule, no press when up by more than 15. Coach had them fall back to a loose zone, no fast break, swing the ball multiple times on offense, only take perimeter shots. Even with that the score kept climbing, since they were hitting the longer shots (of course, those are the shots that won't drop when you need them
)
You could see the girls consciously fighting the urge to fast break on a steal (hard habit to break).