The creepy part of her was when she used the pertrified Setsu as her mastubation tool. Oh, and jumped off the building when her kink is denied.
Creepy was the nicest word I could use to describe such trait. Really
If you really think "being a creepy pervert" is the only thing to Chouko (specially comparing to all the other characters), then we read different stories. It's ok if you dislike Chouko compared to the other girls, but this doesn't make her a "super one-dimensional pervert character". And if we're going with creepiness, what about the yandere Streaker beating people to a pulp?
We don’t even know (yet) whether Chouko aura cover the oddman too. Or she just does not get along with them even post-Setsu
I think that's a fairly safe bet. And regardless of the reasons, it doesn't change the fact that she's a pariah even among them.