When Lennie first sees Curley's Wife, he comments that she is pretty, or "purty." George then warns Lennie to keep away from her. She is, after all, the wife of the boss's very jealous son.
Later in the novel, Lennie is in the barn with a puppy that he has accidentally killed, and Curley's Wife walks in. Lennie tries not to be drawn into a conversation with Curley's Wife, and tells her it's because "George says you'll get us in a mess." He then, at her invitation, starts stroking her hair, commenting "that's nice," before he accidentally breaks her neck after she starts screaming when he strokes too hard.
Before he breaks her neck, he puts his hand over her mouth to muffle her screams, and says angrily to her that "You gonna get me in trouble." This is an echo of the story George earlier related to Slim about Lennie stroking a woman's red dress too hard back in Weed and the woman claiming rape.
In summary, these brief comments are the only comments Lennie makes about Curley's Wife. He tells George that she is pretty, and he tells her that he can't talk to her because she'll get him "in a mess," which he tells her again just before he breaks her neck.
If you're interested in learning more about Curley's wife, I've provided a link to a copy of a letter that Steinbeck wrote to an actress who was playing Curley's wife in a stage adaptation of the story. In the letter, Steinbeck explains the character from his perspective.