Final answer:
The nurse should include the intervention of weighing the client twice weekly in the plan of care due to the significantly low body weight of the client.
Step-by-step explanation:
The nurse should include the intervention of weighing the client twice weekly in the plan of care for a client with anorexia nervosa who is at 60% of ideal body weight. Weighing the client regularly helps monitor their progress and assess the effectiveness of the treatment. It allows the healthcare team to make necessary adjustments to the plan of care for the client.
Encouraging the client to drink 125 mL of fluid each hour while awake would be beneficial for hydration, but it is not the most crucial intervention in this situation. Allowing the client to eat independently in their room may not be appropriate as supervision and monitoring of the client's eating habits and progress are important. Measuring the client's vital signs once each day is a general nursing intervention but may not be specifically related to addressing anorexia nervosa.