Final answer:
The primary nursing diagnosis that the nurse might choose for Mrs. Tan is Nutritional imbalance.
Step-by-step explanation:
The primary nursing diagnosis that the nurse might choose for Mrs. Tan is Nutritional imbalance. Mrs. Tan's frequent refusal of meals and the presence of multiple packages of half-opened cookies and crackers on her bedside table suggest a lack of proper nutrition. This is especially concerning as she is currently being treated for a broken leg and pneumonia, which require adequate nutrition for healing and recovery.