If Mary were sinless, she would have committed a sin when she declared herself a sinner in need of redemption.
If Mary were sinless, the entire word of God would be made a lie. No savior would be needed if even one mortal were able to be born without sin. She had a mortal father, thus she lived a life punctuated by sin.
She did not. She declared Christ her Savior. She said nothing about her sin.
Where in Scripture does Mary declare herself a sinner?