Mary was the human fallen instrument used to produce the incarnation,however
As Jesus said.. Before Abraham was, I AM
Mary was conceived without sin. This is known as the Immaculate Conception. The Immaculate Conception means that Mary, whose conception was brought about the normal way, was conceived without original sin or its stain—that’s what "immaculate" means: without stain. The essence of original sin consists in the deprivation of sanctifying grace, and its stain is a corrupt nature. Mary was preserved from these defects by God’s grace; from the first instant of her existence she was in the state of sanctifying grace and was free from the corrupt nature original sin brings.
When discussing the Immaculate Conception, an implicit reference can be found in the angel’s greeting to Mary. The angel Gabriel said, "Hail, full of grace, the Lord is with you" (Luke 1:28). The phrase "full of grace" is a translation of the Greek word kecharitomene. This word represents the proper name of the person being addressed by the angel, and it therefore expresses a characteristic quality of Mary. The traditional translation, "full of grace," is more accurate than the one found in many recent versions of the New Testament, which give something along the lines of "highly favored daughter." Mary was indeed a highly favored daughter of God, but the Greek implies more than that (and it never mentions the word for "daughter"). The grace given to Mary is at once permanent and of a unique kind. Kecharitomene is a perfect passive participle of charitoo, meaning "to fill or endow with grace." Since this term is in the perfect tense, it indicates a perfection of grace that is both intensive and extensive. So, the grace Mary enjoyed was not a result of the angel’s visit, and was only as "full" or strong or complete as possible at any given time, but it extended over the whole of her life, from conception onward. She was in a state of sanctifying grace from the first moment of her existence to have been called "full of grace."
Since Mary is Jesus’ mother, it must be concluded that she is also the Mother of God: If Mary is the mother of Jesus, and if Jesus is God, then Mary is the Mother of God. There is no way out of this logical syllogism, the valid form of which has been recognized by classical logicians since before the time of Christ.
Although Mary is the Mother of God, she is not his mother in the sense that she is older than God or the source of her Son’s divinity, for she is neither. Rather, we say that she is the Mother of God in the sense that she carried in her womb a divine person—Jesus Christ, God "in the flesh" (2 John 7, cf. John 1:14)—and in the sense that she contributed the genetic matter to the human form God took in Jesus Christ.
"To become the mother of the Saviour, Mary 'was enriched by God with gifts appropriate to such a role.' [LG 56.] The angel Gabriel at the moment of the annunciation salutes her as 'full of grace'. [Lk 1:28 .] In fact, in order for Mary to be able to give the free assent of her faith to the announcement of her vocation, it was necessary that she be wholly borne by God's grace."
Catechism of the Catholic Church