A. That coworker needed a sharp attitude adjustment and I’m sorry they were a dick to you and B. People deserve the respect of having their gender identity recognized. It’s every bit as important as a name, as you indirectly noted, and I’m firmly of the opinion that if you can’t respect people, then you don’t belong in a customer service job, particularly not one where you’re dealing with sometimes very vulnerable young people, as in this case. The student is transgender, and even if my coworker did not know that, she still needed to acknowledge her mistake, learn from it, and not throw a ten minute hissy fit about being required to refer to the student by they/them pronouns. There’s not knowing, and then there’s refusing to do the right thing once it becomes obvious that you’ve made a mistake and covering it all under the guise of “it’s not gramatically correct.” We’ve had that conversation before, she and I, and her insistence on the point is becoming more and more obviously a smoke screen for her being flat out uncomfortable with trans people. So yes, I’m sorry, but that does, in my book, warrant at least someone sitting her down and saying “hey, this is not acceptable.”