[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.