Has anyone ever had a coworker that was great at their job, easy to work with, would help you out if needed and was liked by both management and other coworkers.... until they got promoted to a low or mid level management position and became absolutely shit at their job and blinded by power?

We have this one girl who we all wanted to get a promotion because she worked insanely hard and would have been a good fit for it. Well she got it almost 2 months ago and everyday has been hell. She's become completely disorganized and on a total power trip. I've gotten emails from her scolding me for certain stacks of paper not being in alphabetical order, and I hear from other employees that work closer to her that she frequently leaves stuff for other people to catch up on and nitpicks over the smallest stuff. Maybe it's the nervousness that comes with a new promotion but she's become the literal definition of "micro manager". Just yesterday she told another employee that was trying to make change for a guest who was paying for their room in cash (hotel) that he wasn't allowed to use the petty cash drawer for making change - he had to use his own personal money for it and he would be paid back later. Which is first of all crazy. But more importantly we've NEVER done it like that. She's so eager to "catch" us on stuff we could be doing wrong that she's making up rules on the spot.

Anyone else have stories like this where employees that excel at their job become monster managers? Like switching over to the dark side?