Mary - The co-redemptrix with Jesus
Not yet official because of ecumenical fear but in the 1990's, 4.4 million Catholics from around the world signed a petition to dogmatize this doctrine. In the saint Peter catechism it states:
Question: Did God will to make our redemption and all its consequences depend on the free consent of the blessed virgin Mary?
Answer: God willed that our redemption and all its consequences should depend on the free consent of the blessed virgin Mary.
In the Catholic catechism, number 511, they do claim that Mary co-operated with God in the salvation of men.
511 The Virgin Mary "co-operated through free faith and obedience in human salvation" (LG 56).
This is heresy. Acts 4:12 says that salvation is found in no one else, there is no other name under heaven given to men by which we must saved. If Mary is co-redemptrix then Acts 4:12 is a contradiction and should read that there are two names under heaven given to men by which they must be saved.
In Catholic theology, Mary does indeed save those who will honor and worship her. Catholic theology says that Jesus redeemed us with the blood of His body and Mary redeemed us with the agonies of her heart, suffering in her heart what was lacking in the passion of Christ.
In the Constitution on the Church of Vatican II, P61 in says:
"... in suffering with Him as He died on the cross, she cooperated in the work of the Savior, in an altogether singular way, by obedience, faith, hope and burning love, to restore supernatural life to souls."
This same doctrine is found in every Pope from Leo XIII up to and including John Paul II.
Pope John Paul II said that Mary participates in the redemption achieved by her Son and all graces are granted only through her intercession with her Son.
Again in the Catholic Catechism of 1997, Part 1, section 2, chapter 3, article 9, paragraph 6, it says concerning Mary as Mediatrix as well as prescribing other attributes of God:
969 "This motherhood of Mary in the order of grace continues uninterruptedly from the consent which she loyally gave at the Annunciation and which she sustained without wavering beneath the cross, until the eternal fulfillment of all the elect. Taken up to heaven she did not lay aside this saving office but by her manifold intercession continues to bring us the gifts of eternal salvation . . . . Therefore the Blessed Virgin is invoked in the Church under the titles of Advocate, Helper, Benefactress, and Mediatrix."
Of course there is not even a hint of the idea that Mary was the co-redemptrix with Christ in the Scriptures. This is a flat out invention of the Catholic church. Do you see the consequences of this doctrine? This is putting Mary equal with Christ in regards to redeeming man-kind. This is heresy and will send anyone who believes it to Hell. If you are trusting in Mary for your salvation then you can't be saved. It would be just as useful to trust in your grandmother for your salvation.
Again in the Catholic prayer, The Regina Caeli, salvation is granted through Mary.
The Regina Caeli
O God, who through the resurrection of your Son, our Lord Jesus Christ, did vouchsafe to give joy to the world; grant, we beseech you, that through his Mother, the Virgin Mary, we may obtain the joys of everlasting life. Through the same Christ our Lord. Amen.
Jesus Himself says this about obtaining salvation:
Jesus said to him, "I am the way, and the truth, and the life. No one comes to the Father except through me.
And the book of Acts says that no other name but Jesus is given for men to be saved. Not even Mary.
And there is salvation in no one else, for there is no other name under heaven given among men by which we must be saved."