John Paul II indicated that there was a Messianic fervor at this time. It is NOT a stretch to think Mary fully understood that she was chosen to give birth to the Messiah. Whether or not she realized that He was also God, I doubt. Jewish understanding never seems to have caught on to the fact that the Messiah would be God.
Merry Christmas to you both, first off, and thank you for your questions and skepticism. It enriches us both. It is inevitable that I come off rough at times, but I truly enjoy these arguments and enjoy explaining the Catholic faith.
Regarding Mary's full awareness of her being the mother of the Messiah, the scripture I think leaves that open to interpretation. The verses that relate to the infancy of Christ indicate a degree of confusion. The "do as He tells you" is her last spoken word recorded in the scripture. I think, this word signifies the fullenss of her transition from obedience as a "handmaid of the Lord" to the adoptive mother of Christians everywhere and the type of the Church. On some mystical level one can place her role as the first disciple as early as the Visitation, when she brings the Word to St. John:
My soul doth magnify the Lord. 47 And my spirit hath rejoiced in God my Saviour. 48 Because he hath regarded the humility of his handmaid; for behold from henceforth all generations shall call me blessed. 49 Because he that is mighty, hath done great things to me; and holy is his name. 50 And his mercy is from generation unto generations, to them that fear him. 51 He hath shewed might in his arm: he hath scattered the proud in the conceit of their heart. 52 He hath put down the mighty from their seat, and hath exalted the humble. 53 He hath filled the hungry with good things; and the rich he hath sent empty away. 54 He hath received Israel his servant, being mindful of his mercy: 55 As he spoke to our fathers, to Abraham and to his seed for ever.