Legal action in case of mental harassment and defamation

Hi, There is a girl whom I met year back now, everything went great, families agreed for our wedding. Now her uncle out of ego loss, as he wanted her to get married to someone of his acquaintance is creating problems. Following are the short problems I am mentioned here - He is defaming me, in his network and commenting badly on my family. - Doubting our credentials as a family in society - Torturing a girl for going against me by threatening her they he and his nephew will kill me if I get married. - Brainwashed her dad to take a stand against me. - Abused her and accused her for sleeping with me occasionally (Which we haven't) - She is trying her best to convince them, but they have also threatened to force her and take her home and asked her to quit job. We both are independent working professional belong to same community. (Hindu - Sub cast not mentioning). I am tired of listening to this defamation on my credentials daily. Requesting legal advise on this.