A question about divorce?

My sister is considering divorcing her husband because she has reason to believe that he is cheating on her. The question is, what are the laws regarding divorce? If she initiates the divorce proceedings, can she get alimony from him? And how does his adultery factor in...does she have to have proof? She was told by a friend that it doesn't matter about the cirstances, that whoever is making the most money has to pay the other alimony. How does all of this work? Any insight into this would be much appreciated. Thanks. We live in NC by the way, if that helps any.