Final answer:
The most urgent intervention for a patient with Graves' disease is addressing the elevated body temperature of 101.5°F to prevent the possibility of a thyroid storm.
Step-by-step explanation:
The most rapid intervention by the nurse should be directed towards the patient with an elevated body temperature of 101.5°F, as this could be indicative of a thyroid storm, a serious and potentially life-threatening complication of Graves' disease. While the other symptoms such as a heart rate of 110 beats per minute, fine tremors, and weight loss are also concerning and characteristic of hyperthyroidism, an elevated temperature requires immediate attention to prevent more severe complications.