The Bible doesn't mention Mary as co redeeming anyone from sin.
Romans 5:12
Wherefore, as by *one man sin entered into the world,
and death by sin;
and so death passed upon all men,
for that all have sinned:
13 (For until the law sin was in the world: but sin is not imputed when there is no law.
14 Nevertheless death reigned from Adam to Moses, even over them that had not sinned after the similitude of Adam's transgression, who is the figure of him that was to come.
15 But not as the offence, so also is the free gift. For if through the offence of *one many be dead, much more the grace of God, and the gift by grace, which is by one man, Jesus Christ, hath abounded unto many.
16 And not as it was by one that sinned, so is the gift: for the judgment was by one to condemnation, but the free gift is of many offences unto justification.
17 For if by *one man's offence death reigned by one; much more they which receive abundance of grace and of the gift of righteousness shall reign in life by one, Jesus Christ.)
18 Therefore as by the offence of one judgment came upon all men to condemnation; even so by the righteousness of one the free gift came upon all men unto justification of life.
19 For as by one man's disobedience many were made sinners, so by the obedience of one shall many be made righteous.
It is the obedience of ONE, Jesus Christ, not Mary.
Also note that Adam is held accountable for the sin, not Eve.
Eve was deceived, Adam knew better and did it anyway.
It implies that she had just as much to do with co-redeeming as Eve had to do with bringing about mankind into the realm of sin.
Paul already makes half of the connection by calling Jesus the New Adam. Certainly, this would make Mary the New Eve, the woman mentioned in Genesis 3:15, the woman mentioned at Cana and the foot of the cross. As Simeon said, a sword would pierce her heart. TWO people's hearts were pierced at Calvary for the sake of the Father's will in heaven. Mary will be called blessed by all generations...
It is the obedience of ONE, Jesus Christ, not Mary.
Yes, and as Adam's sin condemned man to death, Jesus work on the Cross redeemed men. However, as Eve participated, was present, was more than a bystander to Adam's action, so did Mary. Neither females were necessary in their scenarios, but it was God's will that they participate and were present. They added nothing to the male's respective work, but just the same, God had them both there. Thus, we can say that Mary was a co-redeemer. There is a lot of deeper meaning to Mary, which is why one would be better served meditating on what exactly was her role and her continued role as being the woman of enmity against the "serpent" even today.
Regards