I think in parsing words and examining speech patterns no point is proved. Word usage varies from translation to translation. The point is this: God gave each and every one of us free will. Like Mary, at any given moment we can say yes or no to God. Like Mary, we can choose to be vessels of God's grace and salvation (although in her situation it manifested in His physical being).
When we are full of God's grace, as the devout Jewish girl Mary was, then we submit to God's will more fully. Yet to say that none of us have a choice in the matter takes this discussion to an entirely different place. It becomes an issue of the nature of God Himself.
Parsing of words? How can you say that? You brought it up, so show me the different translations have it different. I have read them and I don't see where God gave Mary a choice.
Luke 1:31 "You will..." NIV Luke 1:31 "And, behold, thou shalt conceive..." KJV