While there are some bishops who call Mary “Co-Redemptrix,” this term is not found in the Catechism. Mary is referred to as Mediatrix, but only in the sense that she intercedes for us to Jesus. Nowhere does the Catechism state that Mary intercedes to the Father. It is Jesus and Jesus alone who is our Mediator to the Father.
We constantly seek for help from Heaven - the sole means of effecting anything - that our labours and our care may obtain their wished for object. We deem that there could be no surer and more efficacious means to this end than by religion and piety to obtain the favour of the great Virgin Mary, the Mother of God, the guardian of our peace and the minister to us of heavenly grace, who is placed on the highest summit of power and glory in Heaven, in order that she may bestow the help of her patronage on men who through so many labours and dangers are striving to reach that eternal city. …..showing that the Catholic Church has always, and with justice, put all her hope and trust in the Mother of God. SUPREMI APOSTOLATUS OFFICIO ENCYCLICAL OF POPE LEO XIIION DEVOTION OF THE ROSARY
Mediatrix of all Graces 1921 Pope Benedict XV We are then, it will be seen, very far from attributing to the Mother of God a productive power of grace - a power which belongs to God alone. Yet, since Mary carries it over all in holiness and union with Jesus Christ, and has been associated by Jesus Christ in the work of redemption, she merits for us de congruo, in the language of theologians, what Jesus Christ merits for us de condigno, and she is the supreme Minister of the distribution of graces. Jesus "sitteth on the right hand of the majesty on high" (Hebrews i. b.). Mary sitteth at the right hand of her Son - a refuge so secure and a help so trusty against all dangers that we have nothing to fear or to despair of under her guidance, her patronage, her protection. (Pius IX. in Bull Ineffabilis).
Looks like to avoid one heresy, you cling to another!