I have no degrees in theology or Biblical studies. You could say I am Everyman and no more.
But I'll try to answer your question to me just by using my commmon sense ( FWIW--;-) )
You say that "the Prophets in Scripture were able to perform miracles to validate their own position". I would say that God worked his miracles through the Prophets to validate HIS position. The prophets did not work miracles of their own power. And when I read of the prophets I understand that they knew very well that without God's power acting through them, they had no power at all, and that they submitted their own obedience to God who made the miracles happen, using them as instruments of his Divine Will. I see that Moses got into a little trouble when he mistakenly gave in to his own interpretation of God's will and struck the rock twice instead of just once.
Also, the Prophets acted in the time before the appearance of the Lord Jesus on earth.
OTOH, Mary acted in Cana after the Lord was moving in real time among his people.
And the fact of her Virgin Birth made her a walking miracle--a handiwork of the Father. If St. Paul can refer to us who believe in Jesus as "God's handiwork", then she was the first among us to be such. She was the first believer of his Incarnation--the Word made flesh and dwelling among us.
There are many aspects to be meditated upon in the story of the Wedding Feast at Cana. Scripture tells us that Jesus had just named his 12 Apostles and the next event recorded after that was his appearance with the Twelve and his mother at a wedding feast. Since everything happens as God plans it, Mary became aware of the fact that the wine had run out. She informed her Son. She didn't tell Him what to do. She just gave Him the information. It was his will to act upon it. The Psalms tells us that "whatever the Lord wills, He does". God isn't co-erced by his creatures. In full confidence in her Son, Mary goes to the Chief Steward and says: Do whatever He tells you." These are her words to all of us, and those words are so simple. The Chief Steward listens to her. He does what the Lord tells him to do. And he is the first to witness Our Lord's first public miracle and the opening of Our Lord's public ministry.
So we have the Mother of Jesus acting from the inspiration of the Holy Spirit, the Lord acting on his own power and the guy in charge who listens to her, and obeys the Lord who is privileged to witness the public beginning of the Lord's power among us.
Mary fades into the background because, as the first believer and model for all of us who believe, she "decreases while He increases."
Yet--she remains the one that is "blessed among women" and whom "all generations will call blessed", as St. Luke tells us. Also in Luke, Mary says:
"my soul proclaims the greatness of the Lord, my spirit rejoices in God my Savior. For He has looked with favor on his lowly one"---.
She who bore the Incarnate Word calls herself a lowly one, but blessed because of God's grace. She shows us how we are to be as adopted children of God.
Hail Mary , full of grace. The Lord is with you.
Well, we don't say she was God, so I dunno how that follows. Plus, all the prophets were clear that it was God working through them, not them doing it themselves.
(And I don't mean giving birth to God incarnate, that was not something she stood up and did, but was placed on her by God.)
Again, just like the Prophets...it was not her that was doing it but God doing it through her. But I wouldn't take Mary's will out of the equation either: remember..."Let it be done to me according to thy word." That's an assent, however you slice it. She could have said "no" as Jonah once did.