By the way, "She's just going out the door." would probably be more commonly used
The complete and more formal way of saying the full sentence would be "out of the door"; however "out the door" is fine, as well.
I prefer :"She's just going through / out the door.
I think the use of "of" is incorrect in the sentence you gave.
It is absolutely correct. Omitting it is nonstandard.
Typically confused Contrex. What is it that you are you trying to say, C?
Go ahead and provide proof for your contention.
I really never expected anything better than that, Contrex, but I didn't expect you to so loudly proclaim, "As regards the English language, I know sweet tweet!"