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