How should i handle this accusation?

Well a long story short: We were best of friends. She, her boyfriend and me. I was a better friend to her than him. And she was having some problems in the relationship, i was not aware of them. She dumped him even when he was not willing to break up, and now is spreading that he cheated on her with me, and i am responsible for the breakup. And now i am viewed as a real vamp who steals boyfriends, and i have no idea what to do.......Can you suggest anything?