I have seen this come up on several blogs: people say that they can’t swim the Tiber because of the way Catholics see Mary. Some of the first objections are to the term “Mediatrix of all Graces" They think that Catholics see Mary as an equal to Christ. The confusion is compounded by the term “Co-Redemptrix" that is often mentioned but little understood, thinking that this puts Mary in the position of a second redeemer.
We’re going to deal with the Mediatrix of All Graces first, and then in a separate post I’ll get into the Co-Redemptrix idea.
Let me put this very plainly: Catholics do not believe that Mary is a Mediatrix of All Graces in any way that makes her an equal to Christ. There are some problems of language here. Allow me to explain.
The term Mediatrix of All Graces easily generates confusion. Linguistically, the word Mediatrix as used by the Church, does not quite mean the same thing as a female mediator in modern usage. In my Dictionary of English Etymology, Mediatrix is indeed under the heading for Mediator (Mediatrix doesn’t have an entry of its own). It traces back the original meaning of Mediator as “one who intercedes; intercessor", with an origin in 13th century Old French. This original use of the term is clearly what’s intended in the Catechism.
The Catechism of the Catholic Church does indeed use the term Mediatrix, but please note the context and the reference to the documents of Vatican II. CCC 969 references Lumen Gentium 62 on this subject. Lumen Gentium 62 is the key: "Therefore the Blessed Virgin is invoked by the Church under the titles of Advocate, Auxiliatrix, Adjutrix, and Mediatrix. This, however, is to be so understood that it neither takes away from nor adds anything to the dignity and efficaciousness of Christ the one Mediator. For no creature could ever be counted as equal with the Incarnate Word and Redeemer." This is the truth that Catholics are bound to accept.
The modern use of the word Mediator (“one who mediates by action between two parties at variance") does not work for Mary. The older use of the word Mediatrix (one who intercedes on the behalf of another) does work for Mary.
The word Mediatrix, quite simply, means that Mary is an intercessor and advocate. She may be a Mediatrix of All Graces, but only in so far as she is able and willing to intercede for those graces. She is not, in any way, either a second font or a necessary conduit of such grace.
Now, this issue has been around for a long time. This short post will not lay it to rest. That’s ok. It’s not intended to do that. Rather, I hope to open the door to other questions. So, feel free to ask away if this doesn’t settle the issue for you.

You mean "not" lay it to rest.
It is also true that, through God's grace, and by way of fulfilling His divine plan, she mediates the Savior (who is all graces) into the world by accepting motherhood. In fact, He most often uses mediators to connect with us, when He might acheive the connection directly if He chose.
Great blog idea.
Oops. Thanks, Jim.
"God the Father gathered all the waters together and called them the seas or maria. He gathered all his grace together and called it Mary or Maria. The great God has a treasury or storehouse full of riches in which he has enclosed all that is beautiful, resplendent, rare and precious, even his own Son. This immense treasury is none other than Mary whom the saints call the "treasury of the Lord." From her fulness all men are made rich.
"God the Son imparted to his mother all that he gained by his life and death, namely, his infinite merits and his eminent virtues. He made her the treasurer of all his father had given him as heritage. Through her he applies his merits to his members and through her he transmits his virtues and distributes his graces. She is his mystic channel, his aqueduct, through which he causes his mercies to flow gently and abundantly.
"God the Holy Spirit entrusted his wondrous gifts to Mary, his faithful spouse, and chose her as the dispenser of all he possesses, so that she distributes all his gifts and graces to whom she wills, as much as she wills, how she wills and when she wills. No heavenly gift is given to men which does not pass through her virginal hands. Such indeed is the will of God, who has decreed that we should have all things through Mary, so that, making herself poor and lowly, and hiding herself in the depths of nothingness during her whole life, she might thus be enriched, exalted and honored by almighty God. Such are the views of the Church and the early fathers." [Original emphasis]
Saint Louis Marie Grignon de Montfort - True Devotion to the Blessed Virgin, 23-25
"I avow, with all the Church, that Mary, being a mere creature that has come from the hands of the Most High, is in comparison with His Infinite Majesty less than an atom; or rather, she is nothing at all, because only He is “He who is� (Exodus. 3:14); consequently that grand Lord, always independent and sufficient to Himself, never had, and has not now, any absolute need of the holy Virgin for the accomplishment of His will and for the manifestation of His glory. He has but to will in order to do everything."
-St. Louis-Marie Grignion de Montfort
True Devotion to Mary: 14
(same book as noted above, just a different edition title)
"For Mary is infinately below her Son, who is God, and therefore she does not command Him as a mother here below would command her child who is below her. ... When we read then in the writings of Sts. Bernard, Bernardine, Bonaventure and others that in Heaven and on earth everything, even God Himself, is subject to the Blessed Virgin, they mean that the authority which God has been well pleased to give her is so great that it seems as if she had the same power as God; and that her prayers and petitions are so powerful with God that they always pass for commandments with His Majesty, who never resists the prayer of His dear Mother, because she is always humble and conformed to His will."
ibid: 27