The court will ensure to hear the arguments of both parties to divorce, especially since the divorce is not with mutual consent. Your friend's wife will have to substantiate her claims in Court with proof. However, as long as your friend only shared a legally binding business relationship with his ex-wife post their divorce, he has not committed any crime as such.
Under section 13(1) of the Hindu Law, Cruelty is a ground for divorce by either spouse.Cruelty includes mental and physical cruelty. It is considered to be physical cruelty when one spouse inflicts some physical injury on the other partner. The concept of mental cruelty essentially means mentally torture by the other partner. Mental cruelty can also be said as lack of kindness that adversely affects a person’s health.
There exists a possibility that your friend's wife can state that her husband being in regular contact with his ex-wife was mental cruelty towards her.
Hope this helps.