Lenny,
Perhaps your wife should see an allergist. Or just have your doctor test for allergies. I'm not really sure what they do. But this is my best guess at the moment.
Does your wife always drive with the radio on? If there's something screwy with the audio (especially after being in service for who knows how long) it could be producing high frequency audio that some people are sensitive to.
Does she wear glasses? If she wears glasses except when she drives, or only when she drives or reads, this could be a problem as well. Hope some of this helps.

Kevin