that doesnt mean she is sinless
especially when she herself said she had a savior
sinless people do not need a saviour
you keep avoiding what it says
"Jeremiah 1:5 (ESV): "Before I formed you in the womb I knew you, and before you were born I consecrated you..."
or John the Baptist, who received the Holy Spirit when he was just a 6-months-young'un in the womb of Elizabeth.
The difference with Mary was just a matter of he being a few months earlier, even, than John the Baptist when it happened: she received His filling with grace when she was conceived. Conception is when human nature is transmitted to the next generation. Therefore she had an unflawed human nature, which is the human nature she transmitted to Jesus --- her Savior.
It has nothing to do with any kind of "personal merit" as if she had earned it. It has everything to do with God's predestining her to be the one to supply His human nature by her maternity.
Therefore the Angel of God addressed her with the unique title "She who is full of grace," which would have been a lie if she were a sinner.