Is it ok for a pastor to continue to wed a person who is in an emotional affair?

The pastor has talked to all parties involved. The groom is in an emotional affair with a friend of mine, and has professed that he's in love with her. However he's still getting married this Saturday to his fiancee. He's been in this emotional affair for about a year, though I came to this knowledge in the last few days, and has stayed with her till 4 or 5 in the morning every weekend while lying to his fiancee that he was with family and male friends. The bride doesn't know any of this. I don't feel that I can know this and be ok with it- though there is little I can do about it. I don't know the groom or the bride to my knowledge though I did go to high school with them (big school- and it was almost 3yrs ago). I too am engaged and I would be devastated to know that my fiance was carrying on an affair regardless if it were physical or emotional. From what I've gathered in studying the bible God doesn't like divorce. So how can the pastor know that this boy (18) is in love with my friend and his fiancee and still wed them!??!? I don't see this going well as he's not going into this 100% in love and committed to his bride. What can I tell my friend? How can I help get God back involved in this?