Short period Marriage

Dear leagal experts,

Kindly give your advice, I am writing here behalf of my friend, He is 33 year old woking as lecture in college. Recently married a girl of 30 year (working in IT company) as per Hindu rituals. The girl is working since 8 years. from the first day of marriage, there is no marital relation with couple. Both lived together only seven days. She always talking or messaging to someone even in midnight. My friend come to know she has an affair with his male collegue. He saw all the messages between her wife and the guy. When asked about this, she said she is in love with the guy, and she replied that she cannot live with my friend anymore, she left the my friend's house. This is unconsumated marriage, Please advise us how to come out from this marriage. What should be done immediately.

Thanks and regards
K.Saravanan