I seem to vaguely remember something about that, but I have a playthrough for each girl individually, including Tiffany and Chelsea (in hopes they'll show up again at some point and become full-blown LIs). I do remember references to cheating (like on the Tiffany path), but I thought that wasn't there for the faithful-to-Chelsea path. Can you indicate where that text is referenced when you're faithful? I must be missing something, because when he talks about leaving her, he specifically says he "did the right thing" and doesn't mention cheating. Was there another scene where he says he cheated, even when he didn't?