Mary’s first intercession to our Lord Jesus Christ!
My teetotalling coworkers would have preferred for Him to reply, “Mother, there is already too much drunkenness at this feast, and I will not contribute to the guests’ further inebriation!”
(How did Mary His mother know of Jesus’ miraculous powers?)
Did you see The Passion of the Christ? There were some hints in it.
Also. remember Simeon’s prophecy? She knew from the very beginning, in fact, at the Annunciation that everything was special — Holy Spirit involved.
I really can’t answer your question since I wasn’t alive then.
Maybe she was not anticipating a miracle, but rather that he would do something practical about the issue. For example, perhaps one of his disciples had commercial connections and could have gotten a wine merchant to cough up the good stock he was saving for the Romans next time they came up-country.