That moment was weird. She waited something like 5 or more years to finally fuck her brother. One of the first thing that come up to her mind is sharing her past sexual experience... That game is pretty well written, but that scene was not. It's really feel forced, the writer needed to do that at that moment for the MC to be able to get back at the teacher, for whatever reason. If there was some hint of a trauma in Haley's past, that would have made sense. I don't understand why he needed that kind of drama, let's hope the following event will be better written and maybe I will understand it.