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...."
Mary was neither ignorant nor presumptuous of Jesus’ powers on earth. She was a very virtuous young woman, but not totally without sin as some believe. There is no Biblical evidence of this as well as the claim of no siblings born to Mary after Jesus birth (yup, there I said it). Mary likely saw much evidence of Jesus’ powers throughout his growing up in her home. At the wedding in Cana, she seemed to be quietly, privately asking him to help out with a big problem that would end in huge embarrassment if they ran out of wine (giving the appearance that these were close relatives or friends). Jesus told her it was not his time to show these powers, but he helped any way in a spirit of “good tidings,” I believe. He allowed witnesses, however. He could have cleared the room, but he didn’t. He wanted it known.
BTW - I like the Kenny and Wynona version, very powerful. It does nothing to diminish Mary or Jesus as Savior of us all. Merry Christmas!