So i need to keep this brief and on a throwaway account. People have been telling me that my gf flirts with other guys and my best friend told me she sees him eyeing his crotch and acts flirtatious around him. I decided to test this out for myself and I made a fake Facebook account, got a lot of friends and i told some people at my school to add him as a friend so it seems like somebody she would know, the mutual friends. He (brian) adds girlfriend as a contact and she accepts asking how she knows him. Brian explains he added the wrong person but should become friends because he's transferring to the university and lives in the area, share similar friends. They talk for a few weeks and my gf never told me about this. They talk about their interests and other stuff and to make sure that she's 100% the cheater i made sure that brian never started a sexual or romantic conversation or even about meeting up. That was all gf. Gf eventually asks him on a date and he asks if she has a bf and she says "its complicated but not really" and that was when i had it. I video called her and she was shocked to see who was on the other end of the line. She says i violated her trust and i was an asshole. She ranted about it on twitter and Facebook which clearly backfired. She claimed i led her on and that i am a scumbag. She pretty much proved she was a cheater yet all of the girls in our friend group and her mom harassed me online until i blocked them. I broke up with her, on Facebook via post when she ranted about it causing a massive flame war within our friend group. She went to the university counselor and now they want to speak to me about it and they're upset with me