Awful feeling LM. I used to really trust my gut, but even that doesn't always work. The worst is being betrayed by a close family member or long time friend or partner.
Nice people often do get burnt...a lot. We hate mistrusting anyone. We expect to be treated the way we treat others. I will never get used to people that hurt others for sport.
What gets me is how some people can believe the lies even when it is proven to be a lie because the person or people were so convincing. I would call that blind faith.
I would say they have some sort of personality disorder. It's very upsetting to have someone telling lies when you KNOW they are doing it and act all innocent. The worse ones are those that twist something they have done to you to make it look like you are the perpetrator. They have no shame. I wonder if they even have a conscience.