That doesn t sound like a stroke. She should see her primary doctor, she may be having migraines, or something else similar. There is not typically loss of sensation in extremities with migraines however. A stroke has lasting deficit, with extremity loss (motor or sensation) being on the opposite side of any facial changes, droops, etc. I have seen 18 year olds have strokes, but they either had some type of condition that predisposed them to a stroke since birth, or are using some type of recreational drug that increases the chance, like cocaine. Unfortunately, strokes in younger people seem to have a poorer prognosis than older people, but that may be because it is seen less in the younger population. Regardless, the only to truly determine the cause of these headaches is to see a physician.