"Thank you, Petronius Nestorius Maximus."
Names are easy to call but harder to prove.
Your contention is that Mary was the mother of the First Person on the Trinity? Really?
What part of hypostatic union do you not get? She is the mother of the hypostatic union. But what is the hypostatic union? Not an abstract thing but a single, undivided Person in two natures, the Second Person. Not two Persons either, but one, because only one was incarnated.