I missed this before, wanted to comment.
"when you had an affair, would it have been useful for your gf to contact that person letting them know they were a bad person who was causing problems for you two?"
* It was a moment of impulse, I'm not excusing it, just context.
* The person whom I had a affair with, was her friend first.
* The person whom I had the affair with, knew the situation ( lies / cheating /blaming ) and in her own way was trying to heal me.
* I've lost the friendship of someone I really care about because of this.
* When it came out, ironicaly there was a virtual cat fight between them. They no longer talk.
* I wanted to come out into the open almost immediately. I felt like such a hypocrite.