Friends wife threatening and blackmailing what action can i take.

I met a paramilitary personnel few years ago who met me as a customer in my business.He proposed me few months ago.I knew him very well so I told him to reply after few dates.I decided to told my parents about him for marriage but few days ago I came to know that he is a divorcee with 2 children's .The children's are in custody of mother who is also working in paramilitary.I immediately ended all relations with that guy.But the problem is that now his wife is threatening me in phone to told my parents about my relation which was just formal relation.Also she would go in my fathers office which is very near to her home.I told her all about myself and family so that she could help me in getting out of this.But she is threatening me.She is already facing disciplinary actions from her department bcoz of her behaviour.Her extramarital relations were basis of their divorce.How can I be safe and secure legally and also I don't want any nuisance in my job.