14For the love of Christ controls us, having concluded this, that one died for all, therefore all died; 15and He died for all, so that they who live might no longer live for themselves, but for Him who died and rose again on their behalf.
16Therefore from now on we recognize no one according to the flesh; even though we have known Christ according to the flesh, yet now we know Him in this way no longer. 17Therefore if anyone is in Christ, he is a new creature; the old things passed away; behold, new things have come. 18Now all these things are from God, who reconciled us to Himself through Christ and gave us the ministry of reconciliation, 19namely, that God was in Christ reconciling the world to Himself, not counting their trespasses against them, and He has committed to us the word of reconciliation.
20Therefore, we are ambassadors for Christ, as though God were making an appeal through us; we beg you on behalf of Christ, be reconciled to God.
21He made Him who knew no sin to be sin on our behalf, so that we might become the righteousness of God in Him. 2 Corintians 5:14-21 NASB
Scripture is crystal clear....only one person has ever been sinless....and that is Christ Jesus, the Son of the Living God.
"He made Him who knew no sin to be sin on our behalf, so that we might become the righteousness of God in Him." 2 Corintians 5:14-21
Christ is Mary's Savior. It's His intervention as Savior which is the source of Mary's righteousness, just as it's the source of our own.