Why does Alice become angry with Charlie now that his intelligence has increased?

Alice becomes angry with Charlie because he's changed. In addition to becoming more intelligent, he's also become less compassionate.... he treats people differently. According to Alice, he's too smart for her and rather condescending.

She slammed down a book she was holding. "All right. You want to know? You're different. You've changed. And I'm not talking about your IQ It's your attitude toward people-you're not the same kind of human being-"

"So do I. But these days I can't talk to you. All I can do is listen and nod my head and pretend I understand all about cultural variants, and neo-Boulean mathematics, and post-symbolic logic, and I feel more and more stupid, and when you leave the apartment, I have to stare in the mirror and scream at myself: `No, you're not growing duller every day! You're not losing your intelligencel You're not getting senile and dull-witted. It's Charlie exploding forward so quickly that it makes it appear as if you're slipping backwards.' I say that to myself, Charlie, but whenever we meet and you tell me something and look at me in that impatient way, I know you're laughing.