Final answer:
The nurse should provide oxygen through a tube in the client's nose if she arrives at the emergency department with difficulty breathing.
Step-by-step explanation:
If the client arrived at the emergency department and had difficulty breathing, the nurse should provide oxygen through a tube in the client's nose (Option 2). This intervention would help alleviate the client's breathing difficulties. The other options are not appropriate in this situation: consulting the health care proxy appointed by the client (Option 1) would not address the immediate breathing difficulty, and inserting a breathing tube while evaluating the condition (Option 4) would be an invasive intervention that goes against the client's request to decline resuscitation.