I have to say I disagree about Norton's lack of emotional presence. I guess they are all pretty lacking but I never felt like Norton was particularly less developed than the two male critics. I'm wondering if your perception is not so actual and more due to the fact that the majority of our POV time is spent among the two male critics, and Norton is emotionally distant from them.
That's a possibility . . . I don't know, it strikes me as odd that Norton simply . . . goes along with sex. I'm not saying that casual sex = no emotions, but I find the way that she's written as implicit of that. Of course, I'm bringing my own experiences to the reading, but the only sense of emotion from her that I found to be an insight into the character was the anecdote about Jimmy, just before she tells the other two about Morini. Maybe it's just that I relate to Espinoza and Pelletier better, but either way, in my experience, a person who takes two close friends as lovers in the same time period are generally people I admit, I am more willing to characterize as emotionally distant. But again, as abstractions, what can really be said about the emotional validity of any of them . . .