The main thing that Curley's wife reveals about herself in chapter 5 is that she has dreams of becoming a movie star and is totally ignorant about acting or about the movie business. All she knows is that some man told her she was a "natural." She tells Lennie:
"Coulda been in the movies, an' had nice clothes--all them nice clothes like they wear. An' I coulda sat in them big hotels, an' had pitchers took of me. When they had them previews I coulda went to them, an' spoke in the radio, an' it wouldn'ta cost me a cent because I was in the pitcher. An' all them nice clothes like they wear. Because this guy says I was a natural."
This explains her behavior around the ranch workers. They think she is "jail bait" and a "tart," a promiscuous underage girl who could cause all kinds of trouble. She is really only trying out her charms and acting ability on the only audience that is available out here. It explains why she devotes so much attention to her makeup and her curls. Lennie doesn't understand what she is talking about. The only man on the ranch who understands her is Slim. He knows she is just a little girl with grandiose delusions, and he pretends to be impressed by her because he is a kind-hearted man and really feels sorry for her. He knows she hasn't a chance in the world of becoming a movie star, and he pities the poor kid for being married to a man like Curley.
Unfortunately, Curley's wife fails to realize that her provocative behavior will lead to her death. The other men know better than to get involved with her. They shun her. But Lennie does not have any self-control, and he completely forgets about George's earlier warning to stay away from this girl.
"Listen to me, you crazy bastard," he said fiercely. "Don't you even take a look at that bitch. I don't care what she says and what she does. I seen 'em poison before, but I never seen no piece of jail bait worse than her. You leave her be."
She approaches Lennie in the barn because he is the only man she can talk to. She also reveals to Lennie that she dislikes her husband and that she feels lonely most of the time. Lennie probably understands little, if anything, of what she is talking about. But he has found her attractive ever since he first saw her in the bunkhouse.
Lennie still stared at the doorway where she had been. "Gosh, she was purty." He smiled admiringly.
The alert reader should realize that this foreshadows serious future trouble.