Girls mother blackmailing me to get marry to her daughter

I met a girl 4 to 5 years back. we were from same cities. initially we used to talk abt each other job that to be rarely(Once in 2 to 3 weeks). but later she proposed me and i told her that 'i cant marry you because of my family, and i cant go against to them'. she said she is also not looking marriage here, shes just want to enjoy, initially i declined but after sometime she convienced me to be in relationship without commitment. i said yes but rarely used to talk to her on phone and meeting used to happen in decades like once 2 to 3 months. later she helped me to get job in my field, that time she spent some money for me near abt 40 to 50k. after tht she started calling me everyday and also used to call me to meet, initially, i used to talk and meet her because i didnt wanted her to feel tht i will not return money or she will think that i m sefish, that i used her for money(and it was not intention also) so i continue talking to her and also started meeting, one day she said she wanted to have sex but i declined because i am not going to marry you but she promised me that she will not ask me also to marry she just wanted to to enjoy. so we had intercourse on few occasions, but she only booked places and all every time, i never forced her to do that. And after some time i was not comfortable to talk to her everyday and meet also because it was increasing like anything, so i told her that 'its not comfortable for me to talk and meet everyday, i cant do that and if you think that i will marry you in return of this then you are wrong, i told you abt my family' she said ' i know dont worry i m not expecting anything from you, i will not do anything such'. But later on she started lieing me so that i will meet her and talk to her, like she is in hospital or she is ill or she is disturbed by her boss, so that i will talk to her and also meet her everyday and if i dont pick up her call then she started fighting and torturing tht why cant i call and msg her everyday(initially we used to talk once in 2 or 3 weeks). it was really disturbing then after sometime i started giving back her money little bit every month because i want to end this. But she was not ready and 1 day her mom called me and asked me to marry her, i told her mom that 'aunty i never told your daughter that i will marry her, she knows about my family, yeah i have taken money but i am returning it every month as much as possible for me'. Her mom didnt said anything that time. But that girl didnt stop, she called me 36 times in 1 hour and she started forcing me to tell my parents abt us, i told her that my parents will never agree and i told you that but she was not ready and i become everydays torture, so i lied that my parents has seen a girl for me, and they said no to you. she didnt said anything but next day her mom called me and started blackmailing me, saying 'if you dont marry her i can take legal action on you, i have all proof that which places you went and it doesnt matter whether you told her abt your family, now convience your family and marry her or else i will come to your house to meet your parents, now a days law is very strict for girls so i will not let you go, i will spoil your life, so quietly marry her' I told my family abt this but i am really worried now, i know i did mistake but it was not my intention, i was always clear from begining. So i need suggestions what should i do now?