Hmm...So she planned to get revenge using that knife, but he reacted faster than her?
If that were the case, her telling him about the kidnapping kind of gave away what she planned to do...But I guess it was more of a multi-layered plan. She knew she couldn't resist temptation/the training he drilled into her, so she was aiming for people outside the elevator to call the cops on him after they find out what happened?
I like how the beginning narration was made out to seem like it came from the guy, but then at the end, turns out it was actually what the girl was thinking. I found that rather interesting.