She is necessarily "of the Atonement" since it was the will of God that she play a necessary part in the atonement or redemption. This is not to say that without her man would have remained unredeemed but that God's plan gave her a large share in the redemptive work. When we address the Blessed Mother, as "of the Atonement," we mean then, that there is some very close bond between the atonement and her, that she belongs to the atonement and the atonement to her. Mary, although her part is in no way similar in nature to that of her divine Son's, cooperated with Jesus Christ, as no other creature did, in his work of reconciling man with God.
Her claim to this high title rests most solidly on the fact that she consented to become, and became the mother of the Redeemer; that she suffered with Jesus during the passion; and that all graces merited for mankind by Christ have come to us through Mary.