I honestly think she realized partway through the season that she didn’t want to end this all with a real fiancé. I think she is a girl who has led a relatively sheltered life, with few boyfriends, and once she started getting all of the male attention, realized that she actually is a hot number and has some good dating years left. I keep thinking back to that weird filler episode where CH basically talked her into staying. I think that’s why she kept Luke and Jed as long as she did, and why she never gave herself fully to some of those truly great guys like Mike, Tyler, and Peter. I wouldn’t be surprised at all if she knew all of Jed’s shit before the final episode was filmed and he was her cover. Get engaged, shit comes out, break the engagement, and Jed gets his own notoriety. Any press is good press, right? I think they were in on it together.