Regarding a girl

I am a doctor doing my post graduation. Recently one girl sent me a facebook request and had displayed her number. I was doubtful so just checked the number. It was a girl of 21 and just started normal conversation. She turned out to be a mad girl i felt she started telling she loves me and all in just 3 days. She harrased to meet me by calling atleast 20 to 30 times. To be safe i told her my wedding has got fixed. Still she tortured me. So to say an end i met her in my friends room there she gave consent for sex and had a protected sex. She was ok after that. After i went to my native for few days she started calling again and torturing and asked me to meet again. I told her my wedding date is fixed so to avoid her still she tortured. I told her cant meet in my friends place she asked me to meet in lodge. There again she gave consent and after she returned in the evening sheeven if by mistake she conceives started blackmailing me that she wil die and i have to marrry her. It was her major mistake of torturing me to meet her and hope she doesnt conceive it was protected sex though...How can I get out of it if she makies it an issue? she is literally torturing me like hell..