My wife gets bad migraines at least once every 2 weeks caused by stress and mainly bright lights how much of a chance could it be neurological or?

Migraine. It does sound like a migraine headache. It is a neurological condition. It is worth being followed by a neurologist since sometimes migraines with aura (weakness, numbness, visual deficits) can look like stroke.
We don't know. The exact cause of migraine is still controversial. Current research suggests that a "migraine generator" exists in the region of certain brain stem structures of genetically predisposed individuals. The migraineur may be sensitized and therefore is more receptive to external and internal stimuli or triggers (stress). Rec.: see a headache or orofacial pain specialist for proper evaluation.