I agree with Chad, I think her two-dimensionalness in books narrated by the others simply shows how they see her. I mean, it's not like she openly shares her angst and worries about the way she's becoming, so most of them just see her in battle-frenzy mode and never know how much she struggles with it. Or, for example in Jake's case, he can't afford to sympathize. Tobias also knows because he seems to be the person Rachel confides in the most, and he never gets on her case or anything about her violence. By the way, it bugs me that later on we get next to no sense of close friendship between Cassie and Rachel. The occasional fashion joke or "aww Cassie likes Jake" does not a friendship make. Cassie should have been one of the people most worried for Rachel, but she never even tried to reach out to her about it. Not that I think trying to talk would have worked, but it didn't work with Marco either and she still made the attempt. Fail, Cassie. Friendship fail.