Elizabeth Mitchell is a great actress because she can play so many characters. She does this in Lost as well! She has pointed this out, and I have noticed this, as have other people: Off-Island Juliet has a completely different personality than On-Island Juliet. She goes from being all smiley and happy to all cool and calm. What happened? Then while watching the beginning of the ep, she was on the island. But I was like, Wait, that's Off-Island Juliet!?! And she's on the island! I think I could pinpoint it--the exact moment she made the switch was when Ben said "you're mine".