Why does my wife got severe headache when her period start?

Why does my wife got severe headache when her period start?
It's migraine headache due to change in hormone levels. She could try: Drinking enough water, because drinking little rises the chance of migraine. Try don't eating things that are known to induce migraine in the time before the period, like: chócolate, cheese, red wine, oranges. Some women get better by taking another birth control pill (if she takes one at all).
Acupuncture is said to help in some cases too.
If these things don't help, taking naproxen (Anaprox (R) or Naprogesic (R) ) starting 3-4 days before the expected period until after the start of the period could bring reliefe. It's like a short-time prophylaxis. Don't take any medication if your're (better - your wife) is allergic to meds or has other diseases. Ask a GP or Neurologist before taking meds for migraine prophylaxis.
Horomone imbalance that takes place at this painful time.
Retaining water can cause headaches along with bloating and other side effects when it comes to the monthly cycle of a woman.
Lotsa thins are going on in her body at that time, hormone imbalances, high blood presure, water retention etc.
A head ache i believe is your body's alarm clock, and its just to let you know that your body is going through some stuff.