If you were training your replacement at your job and your boss was really difficult to work with, would you warn them?
On the one hand, I would hate for them to be blindsided by the insanity that happens, but in the other hand, they would be my ticket out of this place....
I would tell them, "Judy is very particular about how this is done, so ask questions if you're not clear about any part of the process." Wherever applicable and in as many variations as it takes.
The problem is that my boss will tell me to do something, I'll get clarification on what she wants, then once it's done, she'll berate me for doing it and ask why it was done in the first place. When I tell her, "But you asked me to do it that way," her response is usually either "you must have misunderstood me" or "I just expected something different."
She had me make 30 copies of a document for a board meeting, then when I presented her with the copies, she looked at me like I'd grown a second head and asked me, "Why in the world would the board ever need to see this?" I told her she asked me to do it, and she pretended not to hear me, and continued to ask me why I would do that for a meeting. This pleasant exchange took place in front of her twin 12-year-olds.
I have no idea how to warn a new employee about these issues without just simply telling them, "She's crazy, don't take it personally."