No she didn't, because what you are saying is that the Second person of the Trinity did not exist until Mary gave birth to Jesus.
The Second Person of the Trinity preexisted Mary. She gave birth to the incarnation of the second person of the Trinity, but not to His divine nature.
His divine nature was not dependent on her, which is what you are saying happened.
Galatians 4:4. You lose.
No one is saying that Mary is the source of Jesus’s divine nature. What Christians believe is that the divine and human natures united in Jesus from the moment of his conception. There was never a time when Jesus was not the Second Person of the Trinity. Jesus is a divine person with a human nature — and Mary is the mother of that person.
To say that Mary is not the Theotokos (a name Christians have given her since 250) is to say that there was a time that the divine and human natures of Jesus were not united. You are dabbling in the heresy called Nestorianism. You are in way over your head.
Why would you suppose anything so lumpishly pagan? Christianity isn't some Greek myth with Gods and Goddesses spawning everywhere.
The Holy Trinity is eternal and uncreated. It is the central fact of reality.
Christ - who has existed and will exist forever - has entered into full hypostatic union with mankind. He became Man.
That union is forever. Christ will never cease to be both God and Man. That is the Incarnation: an eternal change to The Holy Trinity.
The Holy Trinity chose Mary as the representative of the human race whose acceptance of God's plan would change reality for ever. She is the Mother of God.