Girlfriend forcing to Marry

hello, I am in a relationship with a girl from one and a half year, we were a happy couple for first 6 months , but later on we started having arguments. We were physically involved as well . Like every relationship things change during a period of time . I have committed to the girl for marriage and our families are involved too. But i don't find that l have same feelings for her and i don't feel like talking to her . After noticing my such behaviour of not being the way i used to be before , she blackmails me of sending me behind bars , she had lodged an FIR also against me being not paying attention to her like before. Everytime i speak a little rude to her or ignore talking to her she runs down to the police station and reports against me. She had raised her hand also infront of my parents.Her family is also not ready for this marriage. So am i. As i have lost all the love and respect for her. I am stuck now, as i cant back out from this relation because she blackmails me to drag me in court and send me behind the bars. My only mistake was i got physical with her that was also on mutual consent. Now please help and advice how should i get rid of this girl.