Abusive people wont leave me alone..advise please?

I met up with this guy called Waran, i linked him with my friend Ann. Waran's big brother and mates (one being an abusive ex i was seeing b4) came banging on the door telling me to open up..i was so petrified i had to call the cops and they legged it. The following morning i get a call from his ex threatening me saying she's gonna knock me out if when she see's me. I have only met his ex once..she came to pick up one of my mates from my house and we spoke for a bit. Her justification for shouting at me was "you know me b4 him..how cud u do that", im really confused am i at fault here? i told her that me an waran arent even in a relationship and she came up with "ya because you like whoring around and not committing..i know alot about u..i heard bares" what i do with my life is my business whats it got to do with her? i am confused..i dont know what to do