Mary most certainly did have a decision in the matter:
Luke 1:38 And Mary said, Behold the handmaid of the Lord; be it done unto me according to thy word.
The emboldened words are her positive response in which she said "yes" to God. Mary is not an automaton or a piece of meat. She played an active role in our salvation through her humility. She was the very first follower of Christ.
Mary can be understood as the Mother of God through this simple deduction: Jesus is both God and man. Mary is the mother of both Jesus the Son of God and Jesus the son of man. Therefore, if Jesus is God, then Mary is the mother of God.
When I read a number of the responses to threads like these, it makes me wonder, why still the arguments over “details” of Christian scripture? It is stuff like this that simply gives “ammo” to those who attack Christians.
All Mary did was agree with what God's angel told Mary would happen to her. If Mary would have said, "No" would that have null and void God's message.
I would compare Mary's response to Jonah's response. God brought Jonah around to His way of thinking. Had Mary responded like Jonah, God would have brought her around as well.
Mary can be understood as the Mother of God through this simple deduction: Jesus is both God and man. Mary is the mother of both Jesus the Son of God and Jesus the son of man.
Wrong. While Mary might be the mother of Jesus in His humanity (son of man), she is certainly NOT the mother of Jesus in His divinity (son of God). God (and Christ) exist long before Mary ever came into being. This is the flawed reasoning in the Immaculate Conception.