Control Mastery Theory invites a therapist to think about the function the a symptom for their patients so your question about the purpose of the self- destructive behavior fits right into our model. Weiss believes that such behavior is a maladaptive defense against a feared event or conflict. It will be different in each case. In order to help a patient solve their conflict a Control Mastery therapist would consider what the origin of the conflict was. We would look to see if there was a childhood trauma which was a component of a problem. A CM therapist would try to get information from the patient which would tell us about what the trauma was for the particular patient that was operating at this particular time. This information helps us in to flush out and understand the nature of the patient's problem. We would then try to make a formulation about how the patient will be working in therapy to master and overcome their conflict. The therapist will make a hypothesis about both of this things right from the beginning of treatment. They will modify their hypothesis as new material is revealed and they learn more about their patient. You might enjoy reading the primmer on Control Mastery Theory in the CM forum section of BOL.
I would guess that Caroline's self destructive behaviors were in part a compliance with her parents' negative thoughts about her. They served to keep her in the role of the black sheep of the family. She was in fact the most gifted member of the family with a high potential for success. Her dangerous behaviors which were unconsciously motivated, served to keep her from knowing about and acting upon her potential.
They are a way of making her parents correct and ruining her life. She may be suffering from survival guilt and feel as though she has to put herself in danger in order to avoid feeling better off than her family. Her dangerous behaviors, which were unconsciously motivated served to keep her from knowing about and acting upon her potential.
We will have to learn more about her history as the story unfolds in order to understand the specifics. We would look at what her fears and anxieties are based on, what danger she is trying to avoid, and try to point out the maladaptive part of her action.