My understanding of both Mary as the mother of God and of Jesus dying but not God come from the same source. Us.

I am a person, which means I'm a homo sapiens, the animal that is a human being, and I have a soul, that which makes me a person. Another way of saying I have a soul is that I am a soul. When I die, and my body is rotting in the ground, I will be in eternal life. It will be my soul in eternal life, but it will be me, the same person that is typing this message right now.

I was born a person, body and soul. But I'm called a person, not a body, not a soul. That's just the style of speech we have.

Describing Jesus is different because of the Trinity. He was and is a person, but a different kind of person than we are. He is a Person of the Holy Trinity. He is both God and human, as we are both soul and human. But while it's improper to refer to ourselves as a soul - a soul is a spirit, and I'm not a spirit at this time - it is quite correct to refer to the man Jesus as God.

He is God. In the beginning was the Word, and the Word was with God, and the Word was God. And the Word was made flesh, and lived among us. The Word, God, was made flesh. That flesh, that body, that human, is God.

When Jesus died, God did not die, just as our soul does not die at our death. When Jesus was a fetus in Mary's womb, He was both God and human - the Word was made flesh from the moment of Jesus' conception. So just as we have no problem saying Mary is the mother of Jesus, we have no problem saying Mary is the mother of God. The Word became flesh. The Word was with God and the Word was God.

It's quite scriptural.