This is not normal dude people that love you shouldn't mess with you in this big of a level, and talking to his coworker is such a wild cross in limits, It is affecting his work life too, It is straigth up humilianting op and honestly from my point of view this is way worse than cheating, It is mopping the floor with op's dignity If she comes on the next day and say "It's just a prank bro" It doesn't change the fact that she made op feel horrible and made his place of work feel unsafe just to get a few laughs out of It, actions have consequences, sometimes even more that we can imagine

How do you call the action of someone you were supposed to trust and love going behind your back to talk to a coworker to humiliate you and make you feel bad because their expectations of you weren't true? If you see relationships like this and think It's normal i'm really sorry for you because It migth mean you Haven't had a healthy one yet

No, op's girlfriend is just a dick. Believe It or not women can also have common sense and a healthy sex life with their partners

"TIFU by being victim of mental abuse" that's not really a fuck up, If you told her that you were into dominatrixes would she just start paying for one full time just for her? If she seriously thougth that that stupid fetish fantasy was some kind of cheating than she's insecure as fuck, which is not a real problem on It's own If It weren't for the fact that she acted to punish you by the way she irrationally feels by making you feel insecure and nervous as well, It is textbook manipulative and toxic of her to do that, i've been trapped in toxic relationships before and your girlfriend sounds like a caricature of every single one of them