Hmm. Tough one. Honestly? If it were me, I would straight out tell her, you are not my supervisor and have no place asking these types of questions. I take offense to the way you are acting lately.

That's what I would personally say. But I am also pretty bold. However, you cannot get in trouble by putting her in her place. And this way, you don't need to involve your boss who is too busy anyways. Others may have better advice, but that's what I would do.

I think the built up anger will dissipate if you confront her.