Hi, I would say you are not diagnosing any thing here. You are just stating a symptom called nausea that means having a feeling of vomiting. It would have been nice if more information was forthcoming on the symptoms of headache like whether there is any history of such headaches in the past and did she take any medicines for the present headache. And the symptom of stomach ache is also vague to answer anything. As a future student of medicine, you can take her to a physician and note down how the physician analyses the condition. It will help you in understanding about how to evaluate a patient. I hope the above information helps you. Thanks for writing into healthcaremagic.