"It's all about you, isn't it?"
The truth feels good. Nobody wants to hurt what they love; nobody can help it. But the truth feels good, and you'd never slap someone you didn't care about.
Andrea explains how much she's come to resent and regret this experience, the summer project, believing Cathy when she said -- over and over, she said -- how beautiful Andrea is, how quickly she could see results, how happy she could be in just months, weeks, days. How fast it fell apart when she learned just how many lies Cathy was buried under; how easy it is for Cathy to believe in beauty -- to rhapsodize and remonstrate and promise, promise, promise -- when Cathy is beautiful, and thin, and white.
She tells this truth through a parable. A lie of its own, meant to wound and to cut, the way Cathy's unthinking privileges have led her to lead Andrea in turn out over treacherous ledges and great waterfalls, saying "Don't you worry, I have you. You will be caught, and safe. I would never hurt you." And all this time, Cathy knowing there was no way for her to get hurt, herself.
"It must be so nice to be you. Pretty white girl, living in suburbia, whose biggest concern is finding an eye shadow that doesn't totally wash her out. Take a walk in my shoes for a fucking day: Growing up in the hood, having to hit a drive-thru for breakfast because mommy spent the last of the grocery money on her morning fix. But that's okay. I can always rely on Dad. Wait, I can't, because when I was a baby he was shot to death trying to rob a liquor store. So excuse the fuck out of me if I'm not the model student you want me to be."
Cathy takes her at her word, of course. Of course Cathy assumes this is true, because it fits one of only a few models she has on which to base her picture of Andrea's world. "I had no idea," she thinks, she says, "It really is as bad as the movies. I never could have imagined." When what she means is, "I only could have imagined." Which is why Andrea tells her this story: Because lies only have power when you don't have the facts. The facts are bright.
"We all have our secrets, don't we? I know you're fucking that painter man; I know a lot of things: That you're a self-righteous slut, that your son's a judgmental asshole, and that I'm through with your sorry-ass class, and this whole sorry-ass fucking school."
Andrea leaves, with a surprising amount of dignity intact, and just like that Cathy sees the whole story, from beginning to end. When Cathy was young, her parents took her to church what seemed like all the time. And then one summer, this freak tornado took out a bunch of houses in the next town over, and killed the pastor and his kids. And they stopped going. Freak tornado, out of the summer sky, like truth, like a slap from a friend, and the things you trust fall away. Grownups break your heart, or vanish. Cathy was the pastor, all summer, leading Andrea into fantasies; Cathy was the tornado, ripping those fantasies apart.