my wife just got fired on her 2nd day on the job because she discussed wages with her coworkers

Yesterday at work my wife's new coworkers asked her how much she made and when she told them they found out she made more than them. Fast forward to today when my wife gets to work she finds out that one of the new coworkers quit over the wages and they fired my wife on the spot for discussing wages. What do we do? We live in Illinois