How motives does Steinbeck suggest for her behavior?

I'm thinking that you are referring to Curley's wife since she is the only female character in the book. Curley's wife is so lost, lonely and so insignificant that Steinbeck does not even give her a name. She spends the novel trying to find company under the guise of looking for her husband. Curley is in fact an intensely abusive person with a major case of small-guy complex. The irony is that while she pretends to be looking for Curley, she is actually trying to avoid him. The men on the ranch fear Curley's wife. She is a temptress of sorts and she is a possession of Curly’s (hence her name). She projects undertones of sexuality in almost everything she says. The men are lonely which only highlights her danger. They do not want the bosses son, Curley, to get angry. They simply can't afford to lose their job during a depression.