From a Byzantine hymn:
It is truly meet to bless you, O Theotokos, ever-blessed and most pure, and the Mother of our God. More honorable than the Cherubim, and more glorious beyond compare than the Seraphim, without defilement you gave birth to God the Word. True Theotokos we magnify you!
Her being conceived without original sin is not what makes her holier than everyone else. Eve, too, was created without original sin. The Blessed Virgin was conceived “full of grace,” and throughout her life cooperated with, and grew in, that grace.
Some writers are very effusive in their praise of our Lady, and perhaps exaggerate some of her attributes, but I think it is very sound to assert that her sanctity is above the angels. The great theologian Joseph Pohle writes:
No doubt the sanctity of the Blessed Virgin, while vastly inferior to the created sanctity of Christ, surpasses that of the most glorious seraph and the greatest Saints. … The fulness of grace enjoyed by our Blessed Mother was not complete and perfect at the outset, but developed gradually, reaching its climax at the moment of her death. … Some few theologians hold that Mary attained to perfection of grace … when she conceived her Divine Son. But this theory entails an inadmissible corollary, namely, that she received no increase of sanctifying grace after the Incarnation, neither … during the descent of the Holy Ghost … nor … by the merits of her virtuous life. (Dogmatic Treatise on the Blessed Virgin, p. 28, 34)