Quick clarification: The Catholic faith at no time has ascribed divinity to the blessed virgin Mary. She was and is only human. Anything else is by definition a non-Catholic belief about Catholic beliefs about Mary.
“All Have Sinned”
I pointed to Paul's statement:
For all have sinned…
First things first: to sin (“all have sinned”) is an act. That is, actual sin (personal sin one decides to do: as distinct from original sin, which is a state, namely the privation of grace). So this verse does not concern original sin (and thus not the immaculate conception which is that Mary was exempted from inheriting such a state at all by God—not explicitly that she never committed personal sins).1
Moreover, in context, "for all have sinned" follows, "there is no distinction" (between groups, races, echelons etc. of men). That is to say there is no protected race or class of people: kings, poor, rich, fat, small, large, etc. Such is both the context of Paul's use and that of that which he is quoting (Psalm ).
“In Whom All Have Sinned”
…by one man sin entered into this world and by sin death: and so death passed upon all men, in whom all have sinned.
If this includes even one exception, the word “all” cannot possibly refer to absolutely all human beings (cf. Eccles. 7:20). And that's on a logical and linguistic (not doctrinal) level. One such exception exists, as it happens, since the same author writes that "the man Christ Jesus" (1 Tim. 2:5) never sinned:
2 Corinthians 5:21 (DRB) Him, who knew no sin, he hath made sin for us, that we might be made the justice of God in him.
So there is an implied qualification or exception, and so it cannot be used as a proof that Mary is not an exception (since such would rely on its being absolute).
More importantly, this verse is not using the word sinned in the personal sin sense, but on that fateful day in Eden, we were there in Adam (cf. Heb. 7:9). This is excluded by verse 14:
Romans 5:14 (DRB) But death reigned from Adam unto Moses, even over them also who have not sinned after the similitude of the transgression of Adam, who is a figure of him who was to come.
And of course the "death" spoken of in the context of the New Testament was not merely bodily death, but was moreso the separation from the life of God—grace. Including the 'sweat of the brow' and 'painful childbirth' stuff: in a word, original sin from which Jesus comes to save us (and he doesn't save us from bodily death—at least immediately).
In fact, the Adam - Jesus typology used by St. Paul specifically requires the understanding that we really inherit sin from Adam by his original sin, not just follow after His example (v. 15; cf. v. 14):
But not as the offence, so also the gift. For if by the offence of one, many died; much more the grace of God, and the gift, by the grace of one man, Jesus Christ, hath abounded unto many.
Inasmuch as we are not 'ficticiously' made righteous, we are also not 'ficticiously' having sin without this 'rebirth' in, and being 'fathered' by, a new Adam.
In fact, if anything, the New Testament makes a connection between Mary and the sinless, equivalent to no original sin state of regeneration.
Ephesians 1:3-14 (DRB)
Blessed be the God and Father of our Lord Jesus Christ, who hath blessed us with spiritual blessings in heavenly places, in Christ: 4 As he chose us in him before the foundation of the world, that we should be holy and unspotted in his sight in charity. 5 Who hath predestinated us unto the adoption of children through Jesus Christ unto himself: according to the purpose of his will: 6 Unto the praise of the glory of his grace, in which he hath graced us in his beloved son. 7 In whom we have redemption through his blood, the remission of sins, according to the riches of his grace, 8 Which hath superabounded in us in all wisdom and prudence, 9 That he might make known unto us the mystery of his will, according to his good pleasure, which he hath purposed in him, 10 In the dispensation of the fulness of times, to re-establish all things in Christ, that are in heaven and on earth, in him. 11 In whom we also are called by lot, being predestinated according to the purpose of him who worketh all things according to the counsel of his will. 12 That we may be unto the praise of his glory, we who before hoped in Christ: 13 In whom you also, after you had heard the word of truth, (the gospel of your salvation;) in whom also believing, you were signed with the holy Spirit of promise, 14 Who is the pledge of our inheritance, unto the redemption of acquisition, unto the praise of his glory.
The only other place this Greek word 'to grace' (χαριτοω) is used in the New Testament is in Luke 1:
Luke 1:28 (DRB) And the angel being come in, said unto her: Hail, full of grace, the Lord is with thee: blessed art thou among women.
The verb used in Luke 1 adds to the connection in that it is a perfect past participle (it literally means [O] having been graced).
So if anything, the New Testament ties Mary's gracedness with the Ephesians 1 'fully benefiting from Christ's grace' state, by its use only in these two places, and saying Mary had before Gabriel even got to her.
The Bible doesn't say Mary sinned. And even if it didn't say Christ didn't, or even imply it, it still wouldn't mean He did, or is not an exception.
1 Although the ridiculousness of God beginning a new creation with a pure Adam and Eve setting everything straight only for them, or even one of them, to fall into the sin again as our first parents is virtually impossible, and quite abhorrent and clumsy. Cf. The Council of Trent, Decree on Justification, Canon 23: “If any one saith, that a man once justified can sin no more, nor lose grace, and that therefore he that falls and sins was never truly justified; or, on the other hand, that he is able, during his whole life, to avoid all sins, even those that are venial —except by a special privilege from God, as the Church holds in regard of the Blessed Virgin—; let him be anathema. ”