Mary: a very distinct holiness underlined by Vatican II

It is no wonder therefore that the usage prevailed among the Fathers whereby they called the mother of God entirely holy and free from all stain of sin, as though fashioned by the Holy Spirit and formed as a new creature. Adorned from the first instant of her conception with the radiance of an entirely unique holiness, the Virgin of Nazareth is greeted, on God's command, by an angel messenger as "full of grace"(Luke 1:28), and to the heavenly messenger she replies: "Behold the handmaid of the Lord, be it done unto me according to thy word" (Luke 1:38).

Thus Mary, a daughter of Adam, consenting to the divine Word, became the mother of Jesus, the one and only Mediator. Embracing God's salvific will with a full heart and impeded by no sin, she devoted herself totally as a handmaid of the Lord to the person and work of her Son, under Him and with Him, by the grace of almighty God, serving the mystery of redemption.

Dogmatic Constitution on the Church Lumen Gentium, Chapter VIII §56 promulgated by His Holiness Pope Paul VI at the Second Vatican Council