Final answer:
Katherine's behavior of feeling compelled to steal items she doesn't need, despite having the money to purchase them, is indicative of Kleptomania. It is distinct from eating disorders like bulimia nervosa, which involve binge eating and compensatory behaviors.
Step-by-step explanation:
The psychological disorder that best describes Katherine's behavior, where she feels an urge to take small items without paying even though she has the money to do so, is D. Kleptomania. Kleptomania is characterized by a recurrent and irresistible urge to steal items that are not needed for personal use or for their monetary value. This condition is often related to significant distress, issues with the law, and social problems for the individual.
Anorexia nervosa and bulimia nervosa are eating disorders. Bulimia nervosa is characterized by episodes of binge eating followed by attempts to compensate for the excessive amount of food that was consumed, often through vomiting, fasting, excessive exercise, or the use of laxatives. Prader-Willi syndrome is a genetic disorder, and morbid obesity refers to excessive body weight that increases the risk of health problems.