Elaborate in detail.
Also, chaging quest bits is easy in the debuger
Sierra's quest is pretty simple, I don't think it's changed for years. You catch her running out of gym class, follow her to the bathroom to catch her masturbating and discover she's a futa, say she's fine the way she is (there is also an option to turn her full female but I've never done it), invite her to use your office during breaks and set a spy camera to catch her masturbating again, invite her to your office repeatedly to advance her corruption by performing sexual acts together until she eventually thanks you for helping her be more comfortable with who she is and gives you her panties, awhile after that you can talk to her about framing Karin assuming you've hired her in which case Sierra gives you her house key to come over and take pictures of Karin while she's unconscious which can either be Sierra pretending to have sex with her, Sierra actually having sex with her, or Peter having sex with her.
If you then use those pictures to blackmail Karin it skips her questchain and immediately makes her your ally, which I did since I didn't know she even had her own questchain added at some point, I've always blackmailed her. So I was wondering if anyone knew the correct steps to "roll the quest back" as it were to before I blackmailed Karin and trigger her questchain, assuming that's possible.