The worst part is that it is almost like they can SEE that she can buckle with enough pressure. She's trying to do the right thing, but both Oosawa and Shiori are just like, "Cool, I'll see you another day then." Hell, Shiori didn't back down at all really, trying to get her to immediately into a bedroom after being told to back off. That is about as disrespectful of the relationship as they can be, but Yukino isn't strong enough to completely resist determined advances. They say once a cheater, always a cheater; please, Yukino.... PLEASE prove that wrong.