How much did the Blessed Virgin Mary know about Jesus as God? The Catholic Church teaches that the Holy Spirit revealed to Mary the knowledge of the divinity of Christ and His incarnation, from the beginning of the Annunciation.
When Archangel Gabriel informed her. Mary’s knowledge of Christ’s divinity from that time on is sufficient. “The Holy Spirit will come upon you, and the power of the Most High will overshadow you; therefore the child to be born will be called holy, the Son of God.
Furthermore, this was “confirmed” when she visited her cousin Elizabeth who is pregnant with John the Baptist, who called her the “mother of my Lord”. Right after that passage, we see Mary praising God in the famous Magnificat. For what? It was because she was to be the mother of the Son of God, the Messiah, God the Son, God incarnate, which is precisely why she has been called “blessed”. She obviously knew all this.
Joseph was told by “an angel of the Lord” in a dream Who Jesus was, that “he will save his people from their sins” and that one of His names would be “Emmanuel, which means ‘God is with us’”.
The Three Wise Men, their knowledge that Jesus was Messiah was precisely what caused Herod to try to kill all the infants, so as to kill the Messiah, Jesus.
The prophetess Anna also appeared in the temple at that time and spoke about Jesus’ messianic mission. Not only did Mary and Joseph know full well Who Jesus was, but also all who heard and believed Anna's words.
Simeon’s prophecy confirm this to Mary also and the other aspect of her role as the Mother of God and that she would suffer for it also "that a sword would pierce her heart"
Jesus growing up have probably discussed with His mother that He is God who incarnated through her, that's why the Virgin Mary confidently asked Him for wine for the guests in Wedding of Cana, Jesus first "public miracle" but prior to that Jesus Christ must have done lots of miracle already but was only seen by His mother and foster father St. Joseph at their home.
Was the Virgin Mary sorrowful at the Passion and Crucifixion of Jesus knowing that her Son is God and will resurrect again, she sure was, because even Jesus sweat water and blood in His agony in the garden, Jesus who is already God cannot imagine the pain He will go through, how much more His mother who is only human. Ask any mother, how much pain they would fell when they see their children suffer.
THAT'S WHY THE IMMACULATE HEART OF MARY BECAME MORE IMMACULATE WHEN IT HAS BECOME THE SORROWFUL HEART OF MARY.