Pretty sure I remember the second game having a line of description or something like that that essentially went "she's weak to and gives in easily to men's sexual harassment" even if she was the most pure she could be.Not really. The first game is the only time this really happens and the end of the game sort of suggests it was all her plan. But then in the second game if she's pure, it takes a whole week of basically constant sexual pressure before the horny girl gives in, and in the third game (this one) all the encounters have a lot of build up and the only one that doesn't, you can view in the crystal room that it's not really a cheating thing for her at first.
The only time it's "immediately" and she's a total whore is when she starts the game out as, well, a total whore. Duh.