And she wasn’t without fault; Jesus had to correct her / rebuke her at the wedding when he turned water into wine.
She was far better than average, but not perfect.
I wouldn't use the word fault so much as ignorance and presumption (yes, a sin.) There were several instances when she and Joseph second guess their Lord in his mission: when he was teaching in the temple as a child and they chided Him; when they sought him out to take him away from teaching the multitudes, saying he had lost his mind; and the wedding event that you mentioned.
And we cannot forget the words from the lips of Jesus himself: "Who is my mother?" "These...."