Legal procedure for the below case.

I do not know whether this comes under criminal case, but the other party is considering this under Sec 420 and 406. My marriage was fixed in the month of April and just within 2 weeks we were done with the engagement and marriage date was fixed after 20 days. In this case girl was not ready for the marriage and was giving some reasons for postponing the marriage. But her parents made us understand and she agreed for marriage on the fixed date. But immediately after the engagement she stopped behaving normally and started avoiding my calls and never used to reply to my messages. Just before 15 days of marriage we decided to stop here because of girls behavior . Now girls father said he will be filing a case against us for cheating and fraud and asking 5 lakhs as amount for all the expenses and mental harassment amount. but here girl was not mentally prepared for the marriage and her room mates also said the same thing that she is not mentally prepared for the marriage. In this case they are harassing us by making calls from police station and from lawyers. what can be the best way out with out giving any money as there is no mistake from our side.