Final answer:
The diathesis-stress model helps explain the pattern of symptoms in Deandra's case.
Step-by-step explanation:
The model that helps explain the pattern of symptoms in Deandra's case is the diathesis-stress model. This model suggests that a person may have a genetic vulnerability (diathesis) to develop a disorder, which is then triggered by environmental stressors. In this case, Deandra's father having obsessive-compulsive disorder would be the diathesis, and the emotionally devastating breakup would be the stressor. The combination of these factors may have led to the development of obsessive-compulsive behavior in Deandra.