Catholics and Protestants can argue all day long about the idea of The Immaculate Conception, but the wedding of Cana is not evidence of sin on Mary’s part. You cannot assume that Mary asked Jesus to make wine out of water just to “show off “ the powers of her divine son. Perhaps she just wanted the wedding guests to have more wine. Sinless or not there is no way for you living some 2000 plus years after the fact to claim to know what was in Mary’s heart when she made that request. Jesus’ rebuke to her was possibly just a way to tell her that it wasn’t his time to perform miracles yet. But then again maybe it was time....as he did do as his mother told him.
Jesus’ response to his mother contained a pretty good attributed motive:
“Woman, what have I to do with thee? mine hour is not yet come.”
In other words, stop meddling.
It’s true that Mary’s state of grace did not necessarily mean she wasn’t subject to the ordinary limitations of the human mind. There are any number of situations in Scripture where she clearly had a human intellect that was prone to confusion or misconceptions.