East of Eden Section 4 Discussion: Cathy Again!

In section 4, Cathy begins to fall apart somewhat. She sits in the dark in a little shack attached to the whorehouse because the light hurts her eyes, and she keeps her hands wrapped up because they ache with arthritis. Why do you think Steinbeck had this happen to her? Is she being punished in some way for the evil acts she has committed? Is her latent conscience punishing her?