There are several different ways to read these lines. Is the author trying to heighten the sense of tragedy by describing Curley’s wife’s beauty, fragility and youth? The fact that Steinbeck has made a point of giving Curley’s wife beauty and innocence in death strikes some readers as a little disturbing, as if suggesting that a woman gains true purity only when dead. In life, Curley’s wife’s beauty meant trouble, but in death her sexuality is ‘safe’.
An alternate reading is that Curley’s wife looks peaceful in death because she could never find peace in life. She had a dream of how life should be that was never fulfilled, that could never come true in this world. By emphasising her beauty and innocence in death, the author is reinforcing something Crooks said earlier; that our dreams cannot be achieved in this life. This foreshadows events to come; George and Lennie may also find that their dream is only attainable in death.