In Genesis 3:15, Satan is told that emnity will be placed between "him and the woman" and the woman here must refer to Mary because there was obviously no emnity between Satan and Eve as she has already been seduced; and the SAME emnity will be between her (Mary's) Seed (our Lord) and Satan's seed. The emnity between Christ and Satan is without question Eternal and Immaculate, so if the same emnity is between the Blessed Mother and Satan, it too is Eternal and Immaculate.
All Christian tradition (including protestant) refers to Mary's response to Elizabeth as the "Magnificat" because Mary declare that her "soul magnifies the Lord." The word magnify is not used by chance, but rather by design to convey very simple illustration: a soul that is blemished with the stain of sin CANNOT magnify God, a stained soul can only obscure God.
Yep. For Mary to have the same freedom of choice as Eve, she had to be as free from original sin as Eve. IMHO. And backed by many, many of the Church Fathers.