Final answer:
The information about the patient trying ibuprofen 400mg for her headache should be documented in the Medication History section of the EMR.
Step-by-step explanation:
In this case, the information about the patient trying ibuprofen 400mg for her headache should be documented in the Medication History section of the EMR. Medication History is where healthcare providers record the details of the patient's past and current medications. It helps in tracking the effectiveness and side effects of medications, making it a suitable place to document the patient's experience with ibuprofen.