Final answer:
The most appropriate action for the nurse is to take time to sit and talk with the patient about her inability to sleep.
Step-by-step explanation:
The most appropriate action for the nurse to take when finding a young mother hospitalized for an irregular heartbeat and awake is to take time to sit and talk with the patient about her inability to sleep. This action allows the nurse to provide emotional support and address any concerns or anxieties that may be contributing to the patient's difficulty sleeping. By engaging in a conversation, the nurse can also gather more information about the patient's condition and offer appropriate interventions if necessary.