I think that the whole purpose of the Bell possession was to change Olivia's character. Torv was criticized as a bad actress until Bolivia showed up and viewers realized that she wasn't wooden, just told to play that way. Now people want more of that from Olivia. This was great, especially how it really allowed Olivia to come into her own.
I knew that the little girl was the real Olivia as soon as I saw her. Cutest voice in the world, by the way. As soon as she said "I had to know it was you," my wife cried a bit because our relationship is a lot like Peter's and Olivia's.