The Angel told Mary she would bear a son before her acceptance of it "you will conceive in your womb and bear a son". It was a command of God to fulfill 'Behold, the virgin shall conceive and bear a son, and shall call his name Immanuel'.
So she was not asked nor had the power to refuse, but said "Behold the handmaid of the Lord; be it done to me according to thy word" submitting to the will of God.
No one can stop God's Sovereign will by fiat.
As for 'Queen' have you not seen where she said in the Magnificat 'God my Savior' admitting her fallen humanity, believing the Savior (the Lord Jesus Christ) to forgive her sins like the rest of us?
http://www.patheos.com/blogs/standingonmyhead/mary-queen-of-heaven-the-bible-tells-me-so
Mary Queen of Heaven- the Bible Tells Me So
The Queen of Heaven was a goddess in pagan times, but when we call Mary the Queen of Heaven it has nothing to do with pagan worship. We don’t worship Mary. Check out this post to correct that mis understanding.
Instead Mary as the Queen of Heaven is tied in with the Old Testament concept of the royal household. Because the King had many wives it was impossible for one to be Queen. Therefore the King’s mother served in the role. The Queen Mother sat on a throne at the King’s right hand and helped rule the kingdom. Access to the King would often be through the Queen Mother and she would ask favors from the King for those who asked her. You can see an example of this in I Kings 2: 17-25 where Solomon is on the throne next to his mother Bathsheba.
Solomon is David’s son so, this establishes the analogy of the Queen Mother in the Kingdom of David. We know that Jesus is the Son of David and that he inherits the throne of his father David. His role as such is announced by the angel Gabriel from God Most High. So in Luke chapter one:
You will conceive and give birth to a son, and you are to call him Jesus. He will be great and will be called the Son of the Most High. The Lord God will give him the throne of his father David, and he will reign over Jacob’s descendants forever; his kingdom will never end.
So the “Kingdom of God” or “Kingdom of Heaven” which Jesus talks about all the time is also the Kingdom of his father David. Jesus is the King who’s kingdom will never end, and who is his mother? Mary. If he is the King of the Kingdom of David–the Kingdom of God–also called the Kingdom of Heaven, then she is the Queen Mother of the Kingdom of God, the Kingdom of David, the Kingdom of Heaven, and thus the Queen of Heaven–furthermore, if her son the King’s kingdom will never end we must conclude that her reign as Queen Mother at his right hand will also never end. It is an eternal kingdom.
It’s confirmed in Revelation 12 where “a great sign is given” — we see the woman who is the mother of the child who will rule the whole earth with a rod of iron. She is crowned with stars and with the moon under her feet.
A great sign appeared in heaven: a woman clothed with the sun, with the moon under her feet and a crown of twelve stars on her head. She was pregnant…She gave birth to a son, a male child, who “will rule all the nations with an iron scepter.”
Who else could this be–clothed with the sun, with the moon under her feet and a crown of twelve stars on her head–than the Queen of Heaven? That she is the Virgin Mary is clear as she gives birth to the male child who is the King of Kings. Another take on this here.
So Catholics venerate Mary as the Queen of Heaven. It’s there in the Bible…if you have eyes to see.