Then she couldn't have been His mother - AS GOD. She was His mother as MAN. He had no mother as God. She was mother to Him as human. Yet, the divine still existed independent and yet in complete unity with the human. As I said, a mystery.
She is the blessed mother of Jesus. That's what the Bible calls her. To call her mother of God implies that God had a beginning - which is in itself, as You have said, heresy.
G'night
The fact that the Second Person of the Trinity pre-existed Mary (and in fact created her) is perfectly compatible with her being the mother of the Second Person of the Trinity. The Person that came from her womb was the Second Person of the Trinity. Yes He pre-existed her and created her. But nevertheless, He came forth from her womb. And hence it is true that she is the mother of the Second Person of the Trinity. Moreover, since the Second Person of the Trinity is God, it therefore follows that she is the mother of God.
To call her mother of God implies that God had a beginning -
Only to ignorant and untrained ears.
-A8
She gave birth to Incarnate God the Word.