Blackmailing for suicide or lodge a false fir of ipc 376

I am a govt employee aged 26 years.I was in a relationship with a 36 year old girl with no commitment of marriage, after some time she tell me that she is serious and want to marry me. I refused then she started blackmailing me and come to my village and leave a suicide note against me and my family. In pressure of suicidal threat i say yes to marriage . But after two days of this drama, i surprised with a news that she was married with a gut 14 year ago and there is no divorce between them, i collect marriage photos of them. Then i refused to her to marry because she was already married now she blackmailing me to lodge an fir against 376. What should i do pls help