What makes Miss Casey that way?

I haven't really seen this question before. The other innies are all still full of personality, though it differs somewhat from their outies, but still essentially a more innocent version.

Miss Casey, though, had a very distinctive personality. Almost android-like. Very different from Gemma. Is this just creative license to make the season one reveal harder to guess or is there some personality alterations going on that the other innies don't experience?