“”If one is sinless, one does not need a Savior.””
The sinless was from the Grace of God,thus, A Savior is needed
Here is a good explanation from..
From Saint Thomas Aquinas Summa Simplified...
The Blessed Virgin Mary was a human being descended from Adam by way of carnal generation. She had a human father and a human mother. If she had not, therefore, been chosen to be the Mother of God, she would, like every other descendant of Adam, have contracted original sin at the moment of her conception in the womb of her mother. But because she was to be the Mother of His Son, God preserved her soul from the stain of original sin from the very instant of her conception in the womb of her mother. God did this by infusing divine grace into the soul of Mary at the very instant He crated her soul and united it to her body. He did it in virtue of the merits of Christ. no descendant of Adam receives the grace of God except through the merits of Christ. The Mother of God was no exception to this law of grace. Like every other human being who is descended by carnal generation from Adam, the Blessed Virgin Mary needed to be redeemed by the Blood of Christ. But whereas every other human being needs to be clean sed from the stain of original sin - which he has contracted by way of carnal generation from Adam - the Virgin Mary did not need to be cleansed from original sin. She never contracted this stain of sin. Through the grace of Christ, she was preserved from the stain of sin from the first moment of her conception in the womb of her mother. This is the doctrine of the Immaculate Conception of the Mother of God. Because of the widespread misunderstanding of the meaning of this doctrine, it might be well to mention here that the doctrine of the Immaculate Conception of the Virgin Mary is a different doctrine from the doctrine of Virgin Birth of Christ. the doctrine of the Immaculate Conception means that Mary was preserved from the stain of original sin from the first moment of her conception in the womb of her mother. The doctrine of the Virgin Birth of Christ means that Christ was conceived in the womb of Mary by the Holy Spirit without the agency of any human father.
Where is this stated in the Bible?
But because she was to be the Mother of His Son, God preserved her soul from the stain of original sin from the very instant of her conception in the womb of her mother
Unfortunate, speculation and rationalization without any foundation is scripture.
So God miraculously interrupts the physical inheritance of "original sin" from Mary's mother to Mary? Offcourse, the reality is God miraculously preserved Jesus directly.