Blackmailing for marriage

Hi all, I met a girl in college . She approached me and proposed me. My first instance was like i denid her and tried to make her understand that i dont want to be in relation. But she threatened me that she would comit suicide etc . I have been staying in relation eith her with the fear of her suicide. Once i contact her brother and tried to explain the case but he did not undertsand and took the things in a wrong way and asked to em stay away. I have tried a lot to stay away but the girl has been threatening me woth suicide, slicing her hand etc sending pics of all tnose acts . Now iam in a situation wherein i have to marry her bcos of her blackmailings. I have kept all the pictures if her suicide attempts or other acts. Wenevr in the past i have denid anything like mariage she has tried to commit suciide and i had to agree for the same. However i have not married yet . Could you kindly help how to proceed with legal action as here the promise of marriage isdone by me but on the basis of her blackmails not by choice.