With the wedding and everything, it could be due to stress. Sometimes, women stop ovulating when they go through a stressful period, and when they don't ovulate, they don't get their periods. I would also suggested she go see a doctor. It's most probably not a big deal...she might just need some type of medication to get her cycles back on track. Are you guys trying to get pregnant? If not, the doctor might suggest birth control to regulate her cycles, but if you are, maybe clomid to get her to ovulate. Best of luck with everything!
my suggestion would be to see her doctor for a workup.