Consider the sentence:
She's being obnoxious.
I know what the sentence means: she is not usually obnoxious, but she is right now.
Now, what I'm interested in is why the verb be here in the present continuous form.
My guess: her being obnoxious right now requires her to make an effort (to go against her nature, so to speak), so the stative verb be "becomes" a dynamic one.
Is my explanation correct?