“The Blessed Virgin was eternally predestined, in conjunction with the incarnation of the divine Word, to be the Mother of God. By decree of divine Providence, she served on earth as the loving mother of the divine Redeemer, an associate of unique nobility, and the Lord’s humble handmaid. She conceived, brought forth, and nourished Christ” (Lucem Gentium, Dogmatic Constitution on the Church, 61).
And, further along from Lumen Gentium:
69. It gives great joy and comfort to this sacred synod that among the separated brethren too there are those who give due honour to the Mother of Our Lord and Saviour, especially among the Easterns, who with devout mind and fervent impulse give honour to the Mother of God, ever virgin.  The entire body of the faithful pours forth urgent supplications to the Mother of God and of men that she, who aided the beginnings of the Church by her prayers, may now, exalted as she is above all the angels and saints, intercede before her Son in the fellowship of all the saints, until all families of people, whether they are honoured with the title of Christian or whether they still do not know the Saviour, may be happily gathered together in peace and harmony into one People of God, for the glory of the Most Holy and Undivided Trinity.