I believe she could have declined the honor based on her comment "Behold the maidservant of the Lord! Let it be to me according to your word.”
There is a very important parallel between this passage and the creation story of Genesis 1.
As Mary said "Let it be" so God also said "Let here be".
When God created the heavens and the earth, it was formless and void. (Barren, not producing life.)
Mary was a virgin and, in a manner of speaking also void or barren. (not producing life)
Before the acts of creation, "the Spirit of God was hovering over the face of the waters."
In answer to Mary's question as to how she would conceive without a man, the angel replied, “
The Holy Spirit will come upon you, and the power of the Highest will overshadow you;"
It is the same image.
And, finally, to begin the six days of creation, God said "Let there be light."
And in reference to the birth of Jesus, it is said,
"The people who sat in darkness have seen a great light,
And upon those who sat in the region and shadow of death
Light has dawned.” (Mat 4:16)
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