You can get all the kinks unlocked without it.
Yeah I know but on most of my playthroughs I end up breaking up Louise and Jeremy early so Lena can be her mistress. The ones I usually get to complete the kinks are the threesome ones. And on most of my playthroughs Holly ends up having a high change variable by the time she meets up in Ivy's room in chapter 8. So if Lena chooses to stay, there is nothing she can possibly do to stop Holly from sleepig with Ivy.