The Divine Word became man through Mary:
The Son of God took flesh in the womb of the young immaculate Virgin of Galilee; He received that human body and blood from her which, once transfigured by His Passion and Resurrection, were to become Eucharistic Bread, Bread of eternal life for all the sons of men called to become one body, the mystical body of Christ...
Mary alone witnessed the whole of Christ’s life:
From Jesus’ birth to Golgotha, she is the one who spent the most time with Him. She was His most intimate confidante, and, at the foot of the cross, Mary alone remained unshaken in her faith, before her crucified Son.
The Son of God could call Mary “Mother”:
By virtue of which, Jesus chose to obey Mary and to be brought up by her.
Mary is all powerful over the Heart of her Son and she is also the Mediatrix of divine graces:
Jesus chose Mary to inaugurate his public life ["Do whatever He tells you" (Jn 2: 5), is the advice Mary gives the servants in Cana] and He wants us to go through Mary ["Behold your Mother" (Jn 19: 27)] to reach Him.
In essence, Mary is the being that is most directly united to Jesus her Son, the Verb of Life, as much in the mystery of His Incarnation as in the Redemption of the world.