So this is from the Catechism:
The Fathers of the Eastern tradition call the Mother of God “the All-Holy” (Panagia), and celebrate her as “free from any stain of sin, as though fashioned by the Holy Spirit and formed as a new creature”. By the grace of God Mary remained free of every personal sin her whole life long. “Let it be done to me according to your word. . .
(*** added for emphasis)
Was Mary capable of sinning? Like how Eve was born without sin, but choose to enter into it? Or did Mary have something analogous to what a Protestant may call “efficacious grace,” that is to say, it would have been impossible for her to Sin in light of the grace she had received? (Bible verses to help clarify would be great!)