Getting a divorce is not a problem here, since strong grounds exists in case you file a petition for the same. The real problem is regarding any 498A, 406 IPC or Domestic Violence Act or 125 CrPC case which the wife might file against the husband and his family members.
In order to have some protection, the husband and family members can apply for an anticipatory bail if any FIR is registered against them. In the meantime, the husband must try to collect as much evidence as possible which suggests that the real problem between the parties is the wife having an affair, and not demand of dowry.
This evidence will not only help your friend in procuring bail but also in contesting the Trial.