[I wrote this in response to a blog post.]
I understand Mary’s co-redemptrix role as the equivalent role of Eve to Adam; as the Early Church often proclaimed, she is the New Eve to the Second Adam of Christ.
Eve was the designated “helper” (Genesis 2:18) to Adam. In distrust and disobedience to God, her “no” lead to the fall of man.
Mary is the new designated “helper” to the Second Adam. In trusting and obeying God, he “yes” lead to the redemption of man.
Just as the fall was brought about through a cooperative effort between a man and a woman representing the whole of mankind, the redemption was brought about through a cooperative effort between the two new male and female representatives of the whole of mankind: “So God created man in his own image… male and female he created them” (Genesis 1:27).
When we meditate on the prophesy of Genesis, I think we may come closer to understanding this mystery: “Then the LORD God said, ‘It is not good that the man should be alone; I will make him a helper fit for him.’” (Genesis 2:18) This is said not only of Adam, but of the Second Adam as well.
Hence, she is the new “mother of all the living” (Genesis 3:20) – of those who are eternally alive through Christ. As the Queen Mother to the King, she is now our greatest advocate; she is the “helper” – and thus co-redemptrix par excellence – of New Adam, whose body is the Church, and in whose membership we now share.
Laus Deo.
Regia Ecclesia 
Glad for the new post. Keep ’em coming.
Thanks 🙂 Been a bit busy lately.
Great post! I had heard Mary called the New Eve, but I never understood it until I read your post.
Glad to hear it! I’m honoured to be of service, to you and to Our Lady.
Being a “protestant” follower of Jesus, I give more credence to the recorded words of Jesus and the Apostles than to the Roman Catholic church, whose bishops and councils have contradicted themselves (and whose popes have at times issued edicts that are as embarrassing as Peter’s action in refusing to sit with Gentiles when Jews from James in Jerusalem came to visit – an action that brought a deserved rebuke from Paul). Therefore, as I canvass scripture, and do not find a single reference to Mary as a redeemer, I must disagree with the idea that Mary is a co-redemtrix. But there ARE several references in scripture to Jesus as our redeemer. Sorry, but just as Pope Leo X was wrong to sell indulgences, so the Catholic church is wrong to hold Mary, mother of Jesus, up as an object of our faith. Only faith in Jesus can save our souls. (Romans 5:1-5) That is why Jesus came. Mary was not the “mother of God” because Jesus said “before Abraham was, I am”. Therefore, Jesus’ existence preceded Mary’s existence, and therefore Mary was not the mother of Jesus’ being – she was only the mother of Jesus’ earthly body. That is why Jesus prayed to the Father, “Restore me now to the glory I had with you at the beginning”. John 1:1 reveals that Jesus is the creator of all things that have been made, and this means that Mary, his physical mother, was one of his creations. It is fallacious logic to argue that since Mary is Jesus’ mother and because Jesus is divine (God in the flesh), that therefore Mary is the mother of God. The reason this logic is fallacious is because it presumes that Mary’s motherhood extends to ALL ASPECTS of Jesus’ being. And this is clearly not true, because Jesus stated, “I came from the Father and have come into the world. Now I am leaving the world and going to the Father.” Jesus never stated “I came from Mary.” Mary’s motherhood of Jesus only extends to her being the means by which Jesus entered the world. Mary’s motherhood of Jesus in no way applies to the ORIGIN of Jesus’s being. Therefore, she is not the mother of Jesus’ divinity. She was only the mother of Jesus’ incarnation as a human being.