When George and Lennie are getting to know the crew, they are told that Curley's wife is a flirt. In Chapter 2, the swamper informs them, "Well, I think Curley's married . . . a tart." About two pages later, George recognizes this as a danger and warns Lennie to stay away from her.
Don't you even 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.
Curley's wife is similar to the workers because she is, like them, stuck in a bad situation (being married to Curley). She'd had dreams as well. And, flirt or not, she refuses to be stuck in a house all day. The only people to talk to are the other workers. In Chapter Four, she speaks with Crooks and Lennie. "Think I don't like to talk to somebody ever' once in a while? Think I like to stick in that house all time?"
Curley's wife is an instigator but this results from her miserable loneliness. She loathes and appreciates the opportunity to talk to Lennie and Crooks.
Ever'body out doin' som'pin'. Ever'body! An' what am I doin'? Standin' here talkin' to a bunch of bindle stiffs--a nigger an' a dum-dum and a lousy ol' sheep--an' likin' it because they ain't nobody else."
She is lonely but ignorant enough to insult the only people she has to talk to. She is too flirtatious, bound to cause a problem, especially with such a jealous husband. But despite this and her ignorance, she elicits some sympathy simply because her situation is as deplorable as those of the itinerant workers.