When Crooks and Lennie are talking to Candy about their dream of having land in Crooks’s room in the stable, Curley’s wife comes in. We have already been introduced to her. The men on the ranch avoid her because they think she is trouble. They worry that she is a tease. Her entrance seems to confirm this reputation.
"Any you boys seen Curley?"
They swung their heads toward the door. Looking in was Curley's wife. Her face was heavily made up. Her lips were slightly parted. She breathed strongly, as though she had been running. (Ch. 4)
Curley’s wife, Candy, and Crooks all have one thing in common—they are lonely. They were getting along well until Curley’s wife came in. She tells them that all men are scared, so she can get along with one man, but not a group.
Curley’s wife uses the advantage of her status to be rude to the other men. She is racist to Crooks. He was opening up to the other men, disarmed by Lennie’s honesty and genuine nature, but she turned him into a shell again.
Candy stands up to her, telling her to get out. She turns on him too, telling him the only reason he is hanging out with Crooks (and Lennie) is because he has no money.
Curley's wife laughed at him. "Baloney," she said. "I seen too many you guys. If you had two bits in the worl', why you'd be in gettin' two shots of corn with it and suckin' the bottom of the glass. I know you guys." (Ch. 4)
When the conversation turns to how Curley got hurt, she gets angry. The story is that he got his had caught in a machine. She knows this is not true, and asks Lennie about the bruises on his face. Curley’s wife is irritated that they are not telling her the truth. She teases Lennie, calling him “Machine.” Candy tells her to leave Lennie alone. Curley's wife zigzags from wanting to include herself in the men's lives because she is also lonely to belittling and condemning them.
While the reader often feels sorry for Curley's wife, her treatment of Crooks engenders no sympathy. She treats him terribly, looking down on him because of his race. He tries to tell her to leave, and she tells him he has no right to because he is black.