I agree. Musk obviously doesn’t know Ricardo’s Law of Comparative Advantage, which is worrying in someone who plans to try to operate a volume car factory.
The short answer is that unless his time is worth less than hers, he should keep her.
However, I would also make a second point; if she’s really a PA, then her being away for 2 weeks should not make a difference. Everything should be organised at least that far ahead. It’s as his schedule gets further out that things should be expected to go wrong. I can see this with my own scheduling, which nowadays is by phone. I can remember my appointments for the next two weeks…beyond that it’s cloudy. Unless Musk functions in a vacuum, during the two weeks she was away little things probably started to go wrong which, unchecked, will turn into major foul-ups. But he won’t know that for a while.
Of course it’s easy being an armchair CEO yadda yadda, but Harvard Business School and the like are supposed to teach you this kind of stuff.