Maybe she still dared to contradict him. Or just did bad work. We don't know her side of the story yet
All the articles I read on this seem to imply that sleeping in the office should somehow make you immune to being laid off and that your boss must be a real SOB otherwise... Clearly the story is spun to attack Musk.
it's actually becoming an interesting experiment to see how few employees it might now take to keep Twitter running. Musk seems to have a direct hand in production direction (to understate the obvious), so presumably his final point of regression might just be him and half a dozen engineers. Conceivably, it might still run at this minimally staffed level