Similar happened to me. I dated a woman whose step sister was dating my 2nd cousin (no genetic interbreeding). At some point we had a falling out about her infidelity, but her emotional sway with both her family and mine were more supportive of her story. At first it was just "it didn't work out" but as time passed she decided, for reasons I don't know or understand, that I needed to be punished. She invented several different stories and spread them at the family gatherings I wasn't invited to, and eventually I had both her and her extended family and my extended family first avoiding me, then actively excluding me from communication and visits.

Eventually I learned that she claimed I was touching her daughter and was cheating on her with her coworker (whom I had never even met). I tried to defend myself but it was too late.

Today she has been married and divorced twice, and I have zero contact with any of those involved. I only know her status because Facebook doesn't stop sending me update email despite deactivating that account years ago.

Point is, the whisper network is powerful, and doesn't give a shit about reality.