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.
When you say that Mary gave birth to the Second person of the Trinity you are.
Jesus is a divine person with a human nature — and Mary is the mother of that person.
She is NOT the mother of divinity.
She is the mother of the Incarnation of that Divinity, Jesus physical body.
The title, *mother of Jesus* is NOT a statement in Scripture about the nature of Jesus. That issue is clearly and plainly settled throughout the Bible.
The title is to identify which of the many Mary's in Scripture the Holy spirit was referring to.
There were other Mary's mentioned who were identified by other phrases.
*Mother of Jesus* is only about which Mary the Holy spirit was referring to.