The Catholic Church does indeed teach Mary is co-redemtrix. You’re either spreading a falsehood to protect the false teachings of the rcc or your ignorant on this topic.
There is a movement that has petitioned the Popes to have this title defined by the Church, but it has not happened.
I guess I have a question as to sense or tense....if by Coredemptrix they mean as in co-equal and not severable as to the process of salvation of sinners...then no it is a false hood and heresy. If they mean it in terms of simply a “co worker” and “Part of the team” then I would no have no argument with that; any Christian who ever witnessed (to a sinner who was then saved) might be a kind of “co-redeemer”...though it was the Holy Spirit that ultimately “wooed” the sinnner and the work of the Cross that ultimately sanctified him!
I suspect as I’ve gathered in my discussions in the past that most Catholics see her as co equal and indispensable to the salvation process...though not all! As for the sinlessness of Mary, I don’t buy it...perhaps she was fairly decent for a Hebrew woman descended from David, but she still had the taint of Adam and Eve. Her faith and trust in God as to what he was going to do saved her and it was his grace that saved her! She refers to the “God of her Salvation”....she doesn’t say “I have become equal with God in Man’s salvation”!