See though if they did this, it would have affected her subconsious mind perhaps. She could have said yes, I want to forget about this, but once having made that consious decision there is a good chance that her subconsious is going to move it to remember it for her. It'd be her bodies natural pyschological response to a traumic event. When they did it like they did, it really hadn't had time for the concept to sink in all the way and filter down through the many layers of her memory/mind. If they would have waited and asked her about it and she said yes, she probably would have consiously forgotten it but her subconsious would maybe have remembered. Which, would probably be a worse way to go even, because then she might have trauma associated with this memory but not be able to actively recall the memory, compounding the problem.