Final answer:
The nurse gathering data to support a more flexible visiting hours policy in a pediatric unit is acting as a patient advocate.
Step-by-step explanation:
The nurse who recognizes that the strict visiting hours policy is outdated and begins to gather data to support liberalizing visiting hours based on evidence of better patient care is taking on the role of b. patient advocate. This nurse is actively seeking improvements in hospital policies to enhance the well-being of pediatric patients, indicating a commitment to advocating for patients' needs. The actions the nurse is taking go beyond providing direct patient care and instead involve influencing changes in the healthcare system to benefit patient outcomes.