Since the movie came out, it portrayed the character that was inspired by Jackie in such a bad way, that many people stopped speaking to Jackie in real life. On top of that, Jackie tried but failed to sue the production company for damages. It looked like she was going to have to just take it.
Brad had not seen the movie yet as far as she knew and she was going to try and keep it that way. He knew a lot about her past, but if he saw a movie about it, maybe he would reconsider their future wedding. She needed to make sure that he never saw this movie no matter what.