In John Steinbeck's Of Mice and Menthe nameless character of Curley's wife is described from the very beginning as an agent of trouble. The men are aware of this because of her constant trying to mingle with the field hands, because of her mannerisms which she displays. She openly shows that she likes to be the center of attention. In fact, at one point prior to her death we find out she has a wish for the stage at some point. All this would be fine if she were not targeting the field hands.
When George and Lennie arrive at the farm, she comes in to see them posing in a sensual pose pretending to be looking for someone. These are men who are street smart, malicious at times, and can tell things for what they really are. She may want attention since Curley seems to give her none, but she sends the wrong message when she asks for it.
Her face was heavily made up. Her lips were slightly parted. She breathed strongly, as if she had been running
George notices how Lennie stares at Curley's wife with the naivite that characterizes him. This is when we first see the reaction that she causes on the men:
"Well you keep away from her, cause she's a rattrap If I ever seen one. You let Curley take the rap. He let himself in for it. Glove fulla vaseline". George said disgustingly."An I bet he's eatin' raw eggs and writin' to the patent medicine houses."
Additionally, Candy offers how she simply looks for trouble with the field hands by giving them "the eye". To this George makes a very sad prediction which serves as foreshadowing.
She's gonna make a mess. They's gonna be a bad mess about her. She's a jail bait all set on the trigger. That Curley got his work cut out for him. Ranch with a bunch of guys on it ain't no place for a girl, specially like her.
We all know what happens in the end: Her flirting ways lead her straight to Lennie, who (in his lack of understanding), accidentally kills her. This then leads to Lennie's death at the mercy of George--and the end of their dream altogether.