Taylor Marshall, a Catholic convert, writing here:
Today (December Eighth) commemorates the Immaculate Conception – the Catholic teaching that Mary was conceived without original sin. This often begs the question: If Mary is without sin, is Christ the Savior of His Mother Mary? The Catholic Church answers, “Yes, Christ is the Savior of His Mother Mary.”
Later in the same post, Marshall writes,
Saint Augustine stands in this tradition, writing in the early 400s:
“Now with the exception of the holy Virgin Mary in regard to whom, out of respect for the Lord, I do not propose to have a single question raised on the subject of sin – after all, how do we know what greater degree of grace for a complete victory over sin was conferred on her who merited to conceive and bring forth Him who all admit was without sin — to repeat then: with the exception of this Virgin, if we could bring together into one place all those holy men and women, while they lived here, and ask them whether they were without sin, what are we to suppose that they would have replied?”
St. Augustine, De natura et gratia, Patrologia Latina 44:267
liturgical 
Colin – If Mary was not of sin at the time of His conception, then how could JC have obtained his humanity? Anslem’s doctrine of substitutionary atonment is premised on the understanding that Mary was fully human and was of sin:
“For, granted that the actual conception of this man was untainted and devoid of the sin of carnal pleasure, the Virgin from whom he was taked was conceived ‘amid inquity’ and her mother ‘conceived’ her ‘in sin’ [Ps 51:5] and she was born with original sin since she sinned in Adam, ‘in whom all have sinned’ [Rom 5:12]” – Anselm, Why God Became Man, Ch. 16.
Further, JC was “conceived” by the joining of God (through his Holy Spirit) and Man (though Mary) But if Mary was not of sin, then how could Christ have assumed (and conquered) this sinful nature. If that which has not been assumed, has not been redeemed, (Gregory of Nazianzus), then the immaculate concemption prevents the redemption of our sinful nature.
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Being a Jewish mother, Mary never really believed her son.
Ha hahahaha.
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