Curley's wife, a mere genitive of Curley and the only woman in Steinbeck's Of Mice and Men, represents both the temptations and desires of men and the impediments to the achievement of their dreams as well as the desperation of the Depression in which the alienated must live with the futility of dreams.
In a sense, therefore, Curley's wife becomes symbolic of the emotional and spiritual side of the men, thrawted by the economic situation of the country, the men's separation from family and friends, and the painful awareness of the existential situation. This frustrated and alienated existence causes Curley's wife to act cruelly at times, ridiculing the men and viciously taunting Crooks.
Condemned to the limited view of George and others as "jail bait," Curley's wife, who craves attention, uses her female wiles to attract Lennie, who, according to Steinbeck, represents "the powerful yearning of men." She talks of her dream of being an actress in "pitchers" just as Lennie speaks of his dream of owning rabbits on a farm with George. But, when Lennie inadvertently kills Curley's wife, he also kills his and George's dreams. Her death, then, is the representation of the painful desperation of unfulfilled yearnings.
In Jay Parini's biography of Steinbeck: "Steinbeck explained that she is 'not a person, she's a symbol. She has no function, except to be a foil – and a danger to Lennie.'"
Apparently Steinbeck wasn't prepared to fully develop Curley's wife as a villain. Both she and Curley are relatively flat, two dimensional characters, although by the end of the book we know Curley's wife much better than we do Curley, the ostensible villain.
Steinbeck is accused of being sexist for failing to name Curley's wife. He has nothing to gain by being sexist; so why would he commit such an obvious blunder? Denying her a name merely puts her in a class all her own, that of a foil.
Denying her a name is also a way of emphasizing how she's universally disliked throughout the farm. She has not a kind word for anyone but the puppy.
Her own husband refers to her as "my wife," denying her that level of familiarity in front of the men and by doing so maintaining a wall of formality between himself and them. Maybe the men don't dare refer to her by her name out of fear of offending the hotheaded Curley.
I think far too much is being read into the absence of a name for Curley's wife.