3 year old relationship turning out to be financial threats

I was in a relationship with the girl for almost 3 years. On the promises of marriage the girl involved me too much in the relationship, including financial exploitation. She also forced me for sex stating that we are getting married so it's all okay to happen before marriage too. The girl had also double crossed me in the relationship with another boy in the first year of relationship. But eventually, her parents started looking for a groom and she called me and told me not to call back ever again. Now, I could go to her family and ask them questions, but then a few days later her mother called my father and told him that I am threatening them (Baseless, I never did that). The girl also has calculated some amount that she says I owe her (god knows from where) and is asking me to return money. I want to serve the family a legal notice that I should no further be contacted and her mother and her to be fined for the false promises and slander. Would section 417, 425, 420 be valid here? What other sections and sub sections would be valid? What would be the best way to proceed legally in this case? Could this be taken to a court on moral grounds too? Proofs that I can produce : 1. Letters 2. Emails 3. Photogrpahs