Need help

Hi I have come across a girl from matrimony website and we have been in touch for past ten months. We have grown fond of each other in the recent two months. However In Jan i come to know abt her bad past which I said ok it happened in your early ages and I am OK with it. In Feb her sis was murdered by her husband and I come to know that she lied abt her sis to me cos wat I learned from the news is very diff from wat she told me. By this time I was already in love with her and said is that it or anything else you lied abt. She sweared there is nothing else. But in the recent times I doubt her a lot and out of that I checked her mails and chats from which I found that she cheated and manipulated me from the beginning of time as I could see she was saying live I to so many other guys too. I found this and told her this won't workout btw us so I am moving out buy she threatens me saying I have all your chat mesaages and photos of us. I ll complain to police that you cheated me. I never had s*x with her. We just go to movies and beaches casually. Exchanged kisses and hugs which is mutual. I have her chat history as proof with me. she demands I marry her only or else she threatens me that she would defame me. What should I do now? Pls advice me. How should I be prepared in case she goes to police.?