True, and by which logic Mary's parents were grandparents of God, and believers are brothers of God, and the Jews and Romans killed God. But which is misleading and inconsistent with Scripture. For one, the normal unqualified conveyance of this is that if ontological oneness, while Christ is the Creator of Mary and she contributed nothing to His Deity.
And the Holy Spirit is careful to make that distinction when stating the Christ came out of Israel: "of whom as concerning the flesh Christ came, who is over all, God blessed for ever. Amen. (Romans 9:4-5) And nowhere calls Mary the Mother of God, nor believers "brothers of God," which also sends a confusing message and risks blasphemy.
Such is not the language of the Spirit, who is very careful about giving titles, and refrains from giving glorious titles to mortals, while Mother of God is part of the egregious unScriptural exaltation of one whom the Spirit says little of, and what is said is not even close to the Catholic extravagance, which thinks of mortals way above what is written, contra 1Co. 4:6.
The objection of Ratzinger to Co-redemptrix as contrary to language of Scripture at least, is also applicable to Mother of God though he dare not go that far.
, when asked in an interview in 2000 whether the Church would go along with the desire to solemnly define Mary as Co-redemptrix, then-Cardinal Ratzinger responded that “the response of the Congregation for the Doctrine of the Faith, is, broadly, that what is signified by this is already better expressed in other titles of Mary, while the formula “Co-redemptrix†departs to too great an extent from the language of Scripture and of the Fathers and therefore gives rise to misunderstandings†(53).
He went on to say that, “Everything comes from Him [Christ], as the Letter to the Ephesians and the Letter to the Colossians, in particular, tell us; Mary, too, is everything she is through Him. The word “Co-redemptrix†would obscure this origin. A correct intention being expressed in the wrong way. “For matters of faith, continuity of terminology with the language of Scripture and that of the Fathers is itself an essential element; it is improper simply to manipulate language†(God and the world: believing and living in our time, by Pope Benedict XVI, Peter Seewald, Ignatius Press, San Francisco, 2000, p. 306
First, that Mary is obviously not the origin of the deity of Jesus does not make her not a Mother of God. As I've been repeating ad nausea at this point. Motherhood in its definition does not entail sole authorship. The Fact that the there are two natures in Christ suffice for the definition. To be a Mother is to bear and give birth to a child. This passage (IS 7:14) suffices for the definition of Motherhood of Jesus.
The distinction that Mary is the Mother of God is not undercut by a non-mention of the word Mother in your quote from Romans. Much Like bachelor is an unmarried man a woman who conceives and bears a child is the Child's Mother. There's no way this could not be the case without saying something terribly awkward about Jesus and Salvation.
Who is Jesus? He is the Second person of the Trinity. (Heb 1:3) Jesus is God. At no time is he not God. You cannot separate His person from His two natures. He is always one Person with Two. Since Mary's Motherhood suffices for this Title.
It is also an important reminder that to say otherwise by any reason is to deny some aspect of the union of two natures in one person. No Mary is not the Sole author of the nature of God. She is the source for the flesh of Christ. But she bore a person. She gave birth to the second person of the Trinity. This is why in ad nauseam I'm forced to repeat a basic fact of Christianity.
If you deny this you deny the same reality that gives value to the meaning "God died on the Cross." Because two natures existed in the one person. Therefore, whatever is predicated of the person is predicated of the natures and vice versa.
Scripture calls us Children of God By adoption. This is because the Grace of Christ makes us like Christ, Children of God. When God looks upon His Children He sees the grace of the Holy Spirit at work making them adopted heirs(Jn 1:12-14; Romans 8:14; 1 John 3:2). Not Blasphemy, Jesus himself says something on this hinted new relationship in him (Mt 12:50; Mk 3:31).
You should come out of the cold and recognize that you have a familial relationship with God because of Jesus.
Your quotation of speculation from Cardinal Ratzinger, not doctrine, is in reference to a title I'm not discussing. It is a separate issue from the title Mother of God.