The following article was written by Dave Armstrong on his blog.
This particular controversy stems from a homily from Pope Francis, dated 12-12-19 (see it in Spanish), on the occasion of the Feast of Our Lady of Guadalupe. Crux published an article the next day by Inés San Martín, entitled, “Pope calls idea of declaring Mary co-redemptrix ‘foolishness’”. It stated:
Pope Francis appeared to flatly reject proposals in some theological circles to add “co-redemptrix” to the list of titles of the Virgin Mary, saying the mother of Jesus never took anything that belonged to her son, and calling the invention of new titles and dogmas “foolishness.” . . .
What Francis said Thursday is in line with Cardinal Joseph Ratzinger, the Vatican’s doctrinal chief during most of St. John Paul II’ papacy, and now Pope emeritus Benedict XVI.
Speaking with Peter Seewald for the book-length interview published as God and the World: A Conversation, the then cardinal said: “The formula ‘co-redemptrix’ departs to too great an extent from the language of Scripture and of the Fathers, and therefore gives rise to misunderstandings.”
“Everything comes from Him [Christ], as the Letter to the Ephesians and the Letter to the Colossians, in particular, tell us; Mary, too, is everything she is through Him,” Ratzinger said. “The word ‘co-redemptrix’ would obscure this origin. A correct intention being expressed in the wrong way.”
The radical Catholic reactionary site, Church Militant also posted a similar mistaken article on 12-13-19.
There are several things going on here at once (including misrepresentation), that need to be explained. First of all, the issue of co-redemptrix is mostly one of whether it is the best term to describe what is firmly entrenched in Catholic belief and doctrines: Mary Mediatrix (which can also be grounded in the Bible). The two notions (though one can note certain fine-tuned distinctions) are virtually the same. Both are widely and vastly misunderstood, but co-redemptrix is relatively more misunderstood and much less used in Catholic circles.
Pope Benedict XVI accepts this doctrine (“correct intention” above), and he referred to Mediatrix, for example, in general audiences of 10-27-10 and 3-30-11, and a homily dated 1-1-07. On 2 February 2006: he stated: “Bringing her Son to Jerusalem, the Virgin Mother offered him to God as a true Lamb who takes away the sins of the world. She held him out to Simeon and Anna as the proclamation of redemption; . . .” And likewise, on on 11 May 2007: “There is no fruit of grace in the history of salvation that does not have as its necessary instrument the mediation of Our Lady.” He simply thinks that the term co-redemptrix is not the best one to use to describe this doctrine. I happen to personally agree.
Pope St. John Paul II has used the term co-redemptrix on at least five occasions in the course of his papal teachings (see extensive documentation on this). In his greetings to the sick after the general audience of 8 September 1982: