Sinners need a savior. If Mary was not a sinner, she wouldn't need a savior. Yet in Luke 1 we find she includes herself among those in need of a savior:
"And Mary said: 'My soul exalts the Lord, And my spirit has rejoiced in God my Savior.'" (Luke 1:46-47 NASV)
If she was perfect, Mary would not have acknowledged anyone as her savior. The reason Mary acknowledged her need for a savior is because, "as it is written, 'there is none righteous, not even one.'" (Romans 3:10)
Additionally, we know the wages of sin is death, so if Mary had no sin, she should would be alive today or there would be some record of her being the third person (after Enoch and Elijah) taken to heaven without dying. But you know as well as I do, there is no such account recorded anywhere in church history.
Finally, Mary's Magnificat shows the Catholic idea of Mary as co-redemptrix is flawed. How could a perfect, co-savior possibly need a savior? If Mary is a co-redemptrix, it would mean sinners are redeemed and come to the Father not just through Jesus, but also through his mother Mary. And if that were true, it would prove Jesus a liar when he said in John 14, "I am the way, and the truth, and the life; no one comes to the Father but through Me." (John 14:6) And Peter would have been lying when, filled with the Holy Spirit and referring to Jesus, he proclaimed in Acts 4, "And there is salvation in no one else; for there is no other name under heaven that has been given among men by which we must be saved." (Acts 4:12) "Salvation in no one else" -- you'll have to agree, I think, that the term "no one else" pretty much excludes you, me and Mary. Peace, A
Mary did need a savior and had a savior. She admitted this - My spirit rejoices in God my Savior. She never sinned; that is true. But that is not to say that she did not need a savior. How could she be sinless without a savior? God exists outside of time. See my post #13.