Thanks for all of the input. Her symptom added a new dimension yesterday when she told me that her leg "didn't feel right"--it wasn't exactly numb, but it didn't seem like she had full sensation in it either. In the past she's had odd symptoms reminiscent of MS, but never anything that caused me to insist on medical evaluation (other than the eye pain). At the time I posted them on the "other board", but I don't think the archives go back that far so I can't really track them down, and my daughter doesn't remember any of them.
My neuro's nurse (after 20 years of dealing with MS patients, she's really good with reality checks and the info she has on MS) returned my call yesterday and said that we should start with a work-up by her doctor (pediatrician specializing in adolescents) and see where to go from there. Winnie (the nurse) told me that they could do a full neuro work-up on her ASAP after that if it seemed to be warranted.
My heightened sensitivity to her symptoms was validated by the nurse. While she didn't want me dragging my daughter immediately upon having a strange symptom, she did agree that it's wise to be tuned in to those symptoms because a dx and treatment early in the disease process (if it's there) substantially improves the prognosis.
Now I just have to figure out when I can get her to the doctor . . . being 18, one month from high school graduation, working and playing soccer doesn't leave much time for things like doctor's appointments!