It is de fide dogma that Mary was born free from the stain of original sin, just as Adam and Eve were created justified, sanctified and free from sin. If you want to believe that Mary was also born a Catholic with the indwelling of the Holy Spirit, I won’t say that the Church has said that you CAN’T believe that. Personally, I don’t believe that Mary was never a Jew - I believe that Mary was a Jew that “born again” to become the first Catholic. I understand that many theologians also believe that Mary was born a Catholic – but that is a matter of theological opinion, not Church dogma.
Matt, you keep insisting on a reading that if Mary was conceived with the indwelling of the Holy Spirit that she was necessarily, then, “born a Catholic.” That is an inaccurate understanding. She was, as was her Divine Son, born a Jew. Because of her Immaculate Conception was conceived with - and thus born with - all the graces that one who is baptized into Christ receives. She was “born a Catholic” as much as her Son was. This is not just my belief, but that of the Church, as we see in the promulgation of the papal bull *Ineffabilis Deus * - the entirety of it. Grace is, as the Catechism tells us (cf. #1997) a participation in the life of God. Mary was full of grace by virtue of the merits of her Son from the first moment of her conception. If there is no “indwelling of the Holy Spirit” there is no participation in the life of God, no grace of such a level as to prepare her to be the Mother of God.
Here is my question to you: If the Fall had never of occurred, would Mary have been born as a fully divinized child of God before the Word of God became incarnate?
As John has already said, that is extremely speculative. Since our first parents had sanctifying grace (de fide) which signifies the indwelling of the Most Holy Trinity in the soul, Mary would have been born - as would have all of us - with sanctifying grace, whether or not the Son of God were to be Incarnated or not. If He was to become Incarnate, then all other graces that prescind from that because of her divine motherhood would likewise have been hers.