What does the old man mean when he says Curley's wife has "the eye" in Of Mice and Men?

 Candy tells George that Curley’s wife is looking to cheat. 

The men on the ranch are suspicious of Curley’s wife (who is never given a name) because they think she is looking to cause trouble.  When George first arrives, the old swamper Candy tells him to avoid her because she is the boss’s son’s wife and she gives people “the eye,” meaning she flirts. 

"I seen her give Slim the eye. Slim's a...

 Candy tells George that Curley’s wife is looking to cheat. 

The men on the ranch are suspicious of Curley’s wife (who is never given a name) because they think she is looking to cause trouble.  When George first arrives, the old swamper Candy tells him to avoid her because she is the boss’s son’s wife and she gives people “the eye,” meaning she flirts. 

"I seen her give Slim the eye. Slim's a jerkline skinner. Hell of a nice fella. Slim don't need to wear no high-heeled boots on a grain team. I seen her give Slim the eye. Curley never seen it. An' I seen her give Carlson the eye." (Ch. 2) 

He calls her a tart.  Curley and his wife have not been married long, but she is considered trouble.  George tells Lennie to stay away from Curley.  He is worried that Curley is a trouble-maker, and that Lennie will not understand enough to avoid trouble. 

"I hate that kinda bastard," he said. "I seen plenty of 'em. Like the old guy says, Curley don't take no chances. He always wins." He thought for a moment. "If he tangles with you, Lennie, we're gonna get the can. Don't make no mistake about that. He's the boss's son. …” (Ch. 2) 

While Curley’s wife doesn’t exactly flirt openly, she does spend a lot of time looking for Curley.  She also can’t help but be aware of the fact that the men on the ranch are wary of her, and that her husband is a jealous man.  All in all, it causes conflict.  This is one of the reasons that George tells Lennie to avoid Curley.  Curley picks a fight anyway, and Lennie crushes his hand.  It has nothing whatsoever to do with Curley’s wife.  Lennie has no interest in girls other than the fact that their dresses and hair are soft.