Seeking help for a friend !

Hi , I am seeking Advice for my Friend. He just discovered that his wife is cheating on him with her work colleague. She has decided to leave and break the marriage now without giving any reasons. There were no tension , problems or any hassles in there married life so far, till this thing came up. No fightings, nothing. Now the woman just wants to leave him without giving any reasons but the boy (My friend) does not wants to leave her and is ready to give it a good try and want to bring back things normal, but the woman is pretty wilful on her decision. I want to know that how strong do we stand legally, because in no condition my friend wants to give her a divorce,( They are together for around 12 years now & it was a love marriage after all the family drama and was highly opposed by the families) They got married in 2011.Even on asking again and again she just says that she have no reason to give, which we think is not fair at all on my friends part. She just says I cannot live with you anymore because I dont love you anymore. This does not sounds normal to me being a human being. We are really disturbed and mentally puzzled. Please advice what we can do or what are the chances. Thanks.