Kylie has a flag called "cantgetbetter" which will trigger when you click on her first time with love>=40 and yandere>=25, this flag prevent Kylie from returning to reform path. that mean, when you forming taming harem, any click on Kylie will set this flag and she can't return to reform path.
The only chance to clear this flag is Kylie's 60 love event on yandere path. You must select "Let's do it" on dialog to clear this flag to make Kylie return to reform path. And to trigger this event, you need yandere>=35. If this event was already triggered, there is no other way to return reform path.