There are two ways to save a person from death by quicksand. One is to pull them out of the quicksand. The other way is to prevent someone who would otherwise have fallen in, from falling in.
Both people are saved, not as if by their own “merit”, but by the intervention of their rescuer, their savior.
Mary did not die on the Cross.
She was not the sacrifice given for us.
Her blood was not shed for our sins.
She does not defeat Satan.
Mary has nothing to do with our salvation.