I am pretty sure they state because she is a teen girl who thinks she is "Juliet" they don't want to try and keep her from living life the way she wants.
That's why they feel awful that they have to put her on lock down, and how she resents them for it. That is exactly what they wanted to avoid.
That being said, MC does pretty well hate Zak, and he knows he is going to hurt Emma's feelings, but he hopes it is Emma seeing how he(Zak) is, which she does realize in the Theater, and not after she is truly hurt. But he doesn't know the "bad guy" was still on the loose.
Honestly the weirdest part of all that is MC knowing a teen girl well enough to know they had to let her be. He doesn't have kids and his friends do not seem to either.