Girl Blackmailing me after we had intimate chats and sextings

I met a girl on a dating app(name of which i dont remember). There we shared our wattsapp number and soon started wattsapp chat. Our chat got chat intimate and she shared her nude photos. I would like to mention that i never shared my photos. Then she started lamenting about her being poor,her husband not loving her,her husband harrasing her and all sort of stories. She asked for financial helps which I did. After that her demands went on increasing. When I protested she began to blackmail me that i will come to your house and tarnish your image,i will file a police complain and all sorts of threats. I also received messages on sms and wattsapp through different number which claimed to be her brother and he also threatened me. They are complaining that they will file a police complain that i made a promise to marry her. They are also saying that they have wattsapp proof of that. Kindly help me out of this. They have extoted about 1.5 lakh from me. What should I do?