If considered allegorically, the role of Curley's wife--the only woman--is that of Eve. She is a temptress who disturbs the fraternity of the men, for whenever she enters the bunkhouse, or at least stands in the doorway, preventing the men's passage, Curley's wife is a source of tension: The men worry that they will succumb to her physical allure; they worry that Curley will appear and become jealous and enraged against them.
Once she has tempted Lennie, he sins and kills her--albeit accidentally. At any rate, the death of Curley's wife is the end of the "dream" for Lennie and George and Candy. There can be no Eden for them as George must kill Lennie before he is caught and his soul destroyed. With the death of the child-like Lennie, the innocent dream of having a ranch is also lost.