Promised…
“And the angel said unto her, Fear not, Mary: for thou hast found favor with God.
And, behold, thou shalt conceive in thy womb, and bring forth a son, and shalt call his name Jesus.
He shall be great, and shall be called the Son of the Highest: and the Lord God shall give unto him the throne of his father David:
And he shall reign over the house of Jacob for ever; and of his kingdom there shall be no end (Luke 1:30-33 KJV).” Praised…
“And Mary said, My soul doth magnify the Lord,
And my spirit hath rejoiced in God my Saviour.
For he hath regarded the low estate of his handmaiden: for, behold, from henceforth all generations shall call me blessed.
For he that is mighty hath done to me great things; and holy is his name.
And his mercy is on them that fear him from generation to generation.
He hath shewed strength with his arm; he hath scattered the proud in the imagination of their hearts.
He hath put down the mighty from their seats, and exalted them of low degree.
He hath filled the hungry with good things; and the rich he hath sent empty away.
He hath helped his servant Israel, in remembrance of his mercy;
As he spake to our fathers, to Abraham, and to his seed for ever (Luke 1: 46-55 KJV).”
It would seem that Mary was well grounded in Old Testament Scripture promises.
Mary did know.