We had one in our social circle who was like this. Very manipulative, always telling lies about people to play them off against each other. She was also always falling out with people but when telling us the story, it was always the other person's fault, she had been innocently trying to help them and it was thrown back in her face etc. Once the penny finally dropped though, it makes you doubt everything that has ever been said.
Half of us have backed away from here and it has caused a kind of rift, as we don't want to be tell-tales to the ones who haven't realised yet. Meanwhile she is telling lies to them about us, and why we're backing off.
And surprise, surprise she has cancer now. You feel hateful for thinking it, but most of us don't believe her, especially as she seems to be practically revelling in it. She shaved her head for the 'chemo' stage, wears a cannula in her arm all the time, and constantly tells us how her cheerfulness and positive outlook are an inspiration to others. I've never known anyone be so delighted at having a life-threatening disease. 
I used to have a desire to expose her lies, but life is so relaxed and drama-free without her that I'm happy just to be out of it, and I think that's all anyone can do.
Back away, refute the lies if asked, always tell the truth when asked, and respond to anything they say with 'Really?" Just don't get involved.