578 Jesus, Israel's Messiah and therefore the greatest in the kingdom of heaven, was to fulfill the Law by keeping it in its all embracing detail - according to his own words, down to "the least of these commandments".330 He is in fact the only one who could keep it perfectly.331
Protestantism errs when it equates sinlessness with divinity. The classic example of this error is the response a Protestant on the Internet once gave to the Catholic dogma of Mary's sinlessness, "Of course she sinned! She's only human" ... thus making sin the measure of what makes someone human! Sin never made anyone human; humans weren't made to sin. Sin only makes us less human and more animal.
Mary gave Jesus His HUMAN nature, not His divine nature.. One is not a sinner because He sins, he sins because he is a sinner by nature, that was Adams legacy to his seed. Jesus did not need a perfect,sinless mother, He came into this world to live the life of man, with all its sins and hardships..and that would include a mom that needed a savior . Rom 3:23 For all have sinned, and come short of the glory of God;
1Jo 1:8 If we say that we have no sin, we deceive ourselves, and the truth is not in us.
Rom 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:
1Jo 1:10 If we say that we have not sinned, we make him a liar, and his word is not in us.
At no time did scripture make an exception for Mary
Indeed He is the only one who could keep keep it perfectly on His own, i.e., strength, He being God. That does not preclude Him granting a special grace to someone else in order that he or she may not sin as the Catechism teaches about the Blessed Virgin Mary:
493 The Fathers of the Eastern tradition call the Mother of God "the All-Holy" (Panagia), and celebrate her as "free from any stain of sin, as though fashioned by the Holy Spirit and formed as a new creature". By the grace of God Mary remained free of every personal sin her whole life long.
"Rom 3:23 For all have sinned, and come short of the glory of God;"
That is a general term, infants who die have committed no sin.
"At no time did scripture make an exception for Mary"
Nor does it need to, since the Church is the pillar and ground of truth, which says Mary never sinned.