Yeah, we're all perverts here. Creators have to follow certain rules and codes of a genre, otherwise people don't get what they expect. In Katie's you know how it all ends up but this doesn't mean the MC goes straight into debauchery. It's much more realistic trying to tell the reader considerations and inner conflicts like depression or desperation along with some twists and turns. It may well be that Katie realizes that the road to downfall is not what she actually intended and struggles to regain her old life, in this case staying engaged to Brian could have been the better decision. It would even make a good and exciting story when Katie turns around at a certain point, she's not the same person any more but a strong and independent woman who gained experience for her lifetime.