thank you for your query. the commonest cause of unilateral headache is migraine. It is usually associated with nausea, vomiting, but not always. It can last from 4 to 72 hours at a stretch, as may be so severe as to disrupt work and functioning. However, if your daughter s headache is persisting continuously for 6 weeks, or progressively deteriorating, secondary causes like tumor, vascular abnormality, spondylosis etc has to be ruled out. sore and stiff neck usually point to a secondary cause. If such a patient would have come to me, I would have advised a brain imaging study like MRI, before prescribing any drug. the MRI findings would have decided the further course of action to be taken. In the meantime, some standard analgesics (like paracetamol, aspirin etc) may be given to control the pain. I would suggest you take her to the hospital urgently, if the pain is very severe. The hospital is most likely to do an MRI, which will be helpful in any case. you can go on with your orthopedic referral as scheduled and take the MRI with you. hope i ve been able to satisfy your query. please feel free to contact me further. All the best.