I don't know, I thought all three actresses did such a great job (I can't even decide which was the best!) that I really felt for her character. She made a mistake, a great big mistake that she could never fix. It was realistic. She thought she knew more than she did, and with the imagination of a child prodigy writer, I can see how easily she could make such a lifechanging error. Am I glad she did it? No. Can I see why her sister and Robbie were both unable to forgive her? Yes. But I still liked the character because of the great way she was portrayed as someone who gets trapped for the rest of her life by the guilt she feels over something she can't ever fix. Robbie and Cecilia were the ones who suffered, no doubt, but not looking at Briony's character as a person suffering too is missing out on part of the story. She wasn't the classic villain. She felt badly, she hated herself, its not as if she simply moved on with life after this. She doesn't seem to feel worthy of anything at all anymore.