You can't fix it - once a Quirk is unlocked it's unlocked for good. But don't worry, the only thing it will do in the future is open up more Yandere content for Gwen. If you don't wish to see any Yandere content, you can turn it off in Preferences :)
Viewing post in Corrupted Kingdoms (NSFW 18+) comments
Well, due to what happened at the end of act 1, she became overly attached to you.
If you don't have sex with her a few times every week, she starts to go crazy.
After about a month of no sex with her she becomes damaged.
Up to you how you want to deal with that, disabling the option in preferences or giving her some attention.(I have over 70 in the blowjob stat with her)