I just resaw the scene again (no need to mention that seeing Mrs Mia Wallace again, my hair flew to the ceiling) and the answer is that simple!
We don’t watch Mia from the mirror, Mia is opposite the mirror (if there even exist a mirror in the scene) and in front of her is the camera as toothpickvega said!
Very clever trick, you think that you’re watching the goddess from the mirror but you don’t!
’‘Is that a fact?’’ ‘‘Mia Wallace’’
