We've heard a lot about Kathy so far, and all of it boils down to one thing: She doesn't like anyone. So it's no surprise that Kathy's chapter starts this way: "Kathy doesn't like you. She doesn't know you, but she still doesn't like you" (20.1).
The only person Kathy ever liked in Mrs. Jewls' class was Sammy, the dead rat. Kathy sounds like a lovely kid, doesn't she?
Turns out Kathy has a reason for her dislike of each person in the class. Once she had a cat named Skunks, who she actually liked. Mrs. Jewls told Kathy that Skunks would never run away, but Kathy kept Skunks locked in her closet just in case—and when she opened the closet one day, Skunks took off. That's how Mrs. Jewls earned her spot on Kathy's dislike list.
Of course, Kathy seems a little bit… troubled, shall we say? "The next time I get a cat, I'll kill him. Then he'll never run away" (20.12), she decides.
Kathy has good reasons for disliking other people too, since as far as she's concerned, each one of them was wrong about something. Once. But once is enough for Kathy.
So we know that Kathy doesn't like you, right? Here's why: "She knows that if you ever met her, you wouldn't like her. You don't like Kathy, do you?" (20.29). Well do you?
Ultimately there's something strangely deep about this kid who doesn't like anyone, as the narrator comments, "It's funny how a person can be right all the time and still be wrong" (20.31).