Break Up & Divorce

Why do some people try to justify their bad actions in any way they can?

So my "best friend" (ex friend now) got with my fiancé (now ex) behind my back while telling lies to him about me, saying I was completely over him and feeding me lies about him as well. I found out, kicked her to the curb and told people what happened. Now she has told everyone that "it's my fault because I was horrible to him anyway" lol and trying to justify her doing it. She said I was abusive to him when I wasn't, and says that's why it was fine that she slept with him. And she has basically rewritten history to paint me as the problem. Why do some people just not own up to their actions and have to blame someone else for doing a bad thing?

Why do some people try to justify their bad actions in any way they can?
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