Perhaps you could suggest to the superintendent that it seems to be time to do a Functional Behavior Analysis to determine what is triggering the principal's anxiety?
I won't say this is all unbelievable, because I have seen plenty of school administration behaviors that take the cake, but it is all unacceptable to say the least. I hope your superintendent gets it straightened out for you!
I am with MON, though -- the sweet "noticed you left early, are you ok" email is not about a "nice approach", it's about provoking a response that you can use against her. If you get a nice response (unlikely), that's all well and good and you can leave it at face value, and if you get no response, same thing, but more likely you could get an insane rant and that's ammunition. Made even better by the fact that it was in response to a perfectly nice email of yours.