Hi,
women have migraine issues during, before or after their periods due to harmonal changes. This migraine sometimes can last for a whole day. Since you're saying that not all the time she has this problem, make sure if it's a menstrual migraine.
Some other emotional triggers for migraine are stress, anxiety & fears.
Next Steps
As your wife has no vomiting & nausea, it will not be so serious.don't worry.she can do her check up with a gynaecologist..
Health Tips
if it's not menstrual migraine, it may be due to emotional reasons like stress.. helping her to alleviate the stress will be helpful in long term. any of the relaxation techniques will be very effective.