In order to be pure enough to carry and birth Jesus, Mary had to be born without original sin. Thus, Jesus was also the saviour of Mary.
Why? There's nothing in Scripture that says a sinless nature is a prerequisite for giving birth to Jesus Christ.
Instead, that is part of the miracle -- that God became man and was born of a woman; a woman graced by God, but nonetheless a fallen human being in need of a savior, just like the rest of us.