Girl and her family are blackmailing to me for marriage

Dear all , I m a teacher by profession in private institution, working in small salary. I met with a girl in matrimonial site. She contact to me first , then we start chatting further and become good friends . She decided to meet me first before parents meeting I agreed , she came to me by train aporx 600km of traveling. We spend a good time, I took her for city tour and she stay in my house for 2-3 days then she went and then I sent my family to her home . but my parents did not liked her because we found her past affair very serious and the same i responded to her that our parents are not agree so we can go further she was ok with that. then after some days she said marriage is not possible I understand but plz stay with me like a friend I enjoyed your company" she said that. I again accepted this by thinking that she is a good girl and we could be a friend. this was the case of july 2017 . after 1 month I realized it's not friendship from her side then i drop talking bt then after her lil sis come in the talking that her sis is very disturbed plz talk to her at least as a friend she will be good otherwise she may suicide in depression I supposed ok if talking with her is good for her then ok to save her life...then after some days she came to me again and said ok marraige is not possible ok but at least we can enjoy . this was my mistek we had sex. then she had many pic with me where I am necked my upper body parts. she also had our call recordings of last year. after she went home I again realized what we did. so I quit again fro some time . then after this year she asked me for help for job . I informed that I do not have any contact here I asked to my delhi friends for her job. beside of this she come to me for an interview in my city even after I was not agree . then I said ok and she stay again fro 2 days in my house and went back. this incident was in april 2018. I got engaged in feb 2018 I informed to her that i am going for marriage she said ok it's good and it's about stars . she also asked for marriage invitation , I believed on her and happily invited her. before the 5 days of my marriage she create a issue she had mobile no, of my sasural from my mobile silently and sent them many close and intimate pics and old audio. she successfully destroyed my marriage. I may have a case also from sasural side. as well as this girl and her family and some other their known person are blackmailing to me for marriage to her on the same date. and she is claiming that she is my wife and we allready had married to each other in 2017. during the relationship she had puja in home when i was in office and had one tika in forehead I really did not think once I said ok.. and we had some pics with her tika in my room. now she is claiming that this is sindoor and I married to her.. me and my family are scared plz help me. we do not have money . mother is also suffering with cancer , how can i arrange money. i m having many responsibilities.