I understand what Catholicism teaches, and yet this lack of specification of Mary being the mother of the Divine Christ who created here versus what the normal use of "Mother of God" naturally conveys is the problem. As would be calling the mother of Mary the grandmother of God (and all the way back to Eve), being contrary to the language of Scripture, and its careful distinguishing btwn the Creator and the created.
While in a specified technical sense Mary could be called the mother of God as the bearer of the incarnated Divine creator Son, like as Israel itself could be called the God-bearer as qualified, (Rm. 9:5) yet the uncritical common use of the formal title "Mother of God" is misleading and even a blasphemous use since its normal denotation is that of ontological oneness, while Mary contributed absolutely zero to the deity of Christ, and was not responsible for the Divine nature that makes Him the very Son of God.
In contrast, the Holy Spirit is careful to add the qualifier "according to the flesh" and emphasizes Deity ("and of whom as concerning the flesh Christ came, who is over all, God blessed for ever") when stating that the Divine Christ came out of Israel. (Rm. 9:5)
While "mother of my lord" as specifying Christ can be used, (Lk. 1:43) "Mother" of" and Deity are not to commonly go together, and at best, what Ratzingers states regarding "Co-redemptrix" applies to "Mother of God," as concerns the language of Scripture:
"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).
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)
Joseph (Step-Father of Christ) must have been sinless; too; for him to even be able to TOUCH Mary.
I wonder if the Catholic ‘teacher’ understands that GOD is ONE?