There is no theological absurdity in calling Mary the co-redeemer for it was through Mary’s assent that the Christ became the Son of Man in addition to Son of God. The flesh and blood of the Christ was Mary’s flesh and blood. To the extent that Mary’s role was indispensable in the process of redemption, it would not violate theological underpinnings if she were referred to as the co-redemptrix. She is after all, the Queen of Angels.
This has been discussed at length here and forward. http://www.freerepublic.com/focus/religion/2421970/posts?page=7880#7880 andhttp://www.freerepublic.com/focus/religion/2421970/posts?page=7996#7940
It is not simply the technical aspect of it that is in dispute, but more so what it conveys, and the basis for making doctrine which lacks Scriptural warrant, as praying to Mary surely does.
Using that logic, than St. Ann and her husband would also have to share in be co-redeemers...since they birthed and raised Mary, and then her grandparents and great grandparents...etc. All were essential in bringing about the birth of Jesus.
God alone is taught to be our Redeemer in holy Scripture, specifically God the Son, Jesus Christ. To try to divide His glory in that title with His mother I am CERTAIN, godly woman that she was, Mary herself would find completely intolerable.
In the accounts of Heaven in Revelation, Mary is never mentioned....unless you want to talk about the apocalyptic vision of the dragon and the woman... In the visions of Heaven where Jesus is praised forever and ever...absolutely no mention is made of Mary. Mary is a created being who needed to be saved by the blood of the Lamb, just like you and I—a very very godly woman for sure, but not goddess-like—or someone we can worship and pray to. Not a word in the Bible indicates otherwise.