You said that Jesus did not get His divine nature from Mary. You said He got is human nature from Mary. Only God is divine. Jesus did not get His divine nature from Mary. Mary is not the mother of His divine nature. Ergo, Mary is not the mother of the divine God.
Mary is not the origin of the eternal Word, the Second Person of the Trinity. No one ever believed or said that she was.
Mary IS the mother of Jesus Christ. Jesus Christ is the incarnate Word, the Second Person of the Trinity.
Because Jesus Christ is the Second Person of the Trinity, who is God, Mary is called the “Mother of God.”