I'm not sure if someone has mentioned this before, but I sent the boss girls to the Northern Light. However, I was still able to use all of them as party members before they finished their treatments. Additionally, I was able to send Ophelia, whom I shattered, which I assume is a bug.
Viewing post in WEEKLY RELEASE - v0.19.2! comments
Oh, shoot... I assume you're sending them to rehab from the dungeon? It seems I forgot to do a cleaning check on that part... all fixed for next update, thanks!
As for the Ophelia thing... if you Shattered Ophelia before the rehab update then the game doesn't know that you Shattered her, and so allows you to rehab her. Any girl Shattered after the rehab update won't be rehab-able :)