I do think that the attractiveness of Curley's wife is a significant element in how she is seen by the other men. Indeed, they do see her as attractive. This is indicated in how Candy speaks to George and Lennie about her in their opening conversation. It is also evident in how Slim addresses her as "beautiful" at one point when she enters. Her beauty is a critical element in how Curley believes her to be the object of everyone's attention. It is for this reason that he is paranoid about the other men, in particular, Slim in a conversation between the two men. Curley would not be paranoid to this extent if his wife was not seen as attractive by others. I don't think that this is something that caused her to be unfaithful, but it serves as a source of Curley's suspicious attitude towards everyone else on the farm. Curley's wife's beauty is the source of her fatal encounter with Lennie. It is more because she is pretty and wears pretty clothes and has pretty and soft hair that Lennie is attracted to her. It is not because of anything sensuous or ulterior that he wishes to hold her, but more because of something "shiny" or "soft" that he wishes to hold in his hand. It is for this reason that her beauty ends up becoming fatal for both she and Lennie in chapter 5. This is where her attractiveness becomes an issue, the issue, for all of the characters.