if you reject the term “Mother of God” what exactly do you call Mary? The mother of His human nature? Then did she bear only His human nature? What happened to His divine nature?
The mother of Jesus as the writers of the Gospel did and as moved by the Holy Spirit.
using your logic, would you say the Holy Spirit is the father of God as it was the Holy Spirit who impregnated Mary?
of course you wouldn't.
and to assign a title to Mary not used in the Bible is wrong as well.