The Most Holy Theotokos is the Mother of God, who is the King of Heaven. By virtue of being his mother, she is the queen. She is the first Christian, the first to believe in her own Son for her salvation. She is His mother. Why would she not have a special place in His heart?
The Church celebrates the Feast of the Dormition of the Theotokos on August 15th. The hymns on this day teach us that the Theotokos died a natural death, and was assumed into Heaven by her Son, in the body (i.e., she has attained the Resurrection, no one else...save Christ...has done so). Tradition tells us she appears to the Apostles, after they find her body to be missing from the tomb, and tells them what has happened. This Tradition is very old, almost two millennia. She resides in the heavenly realms, with Christ and the saints, and she prays for us, just as the rest of the saints do so.
When we speak of saints "working miracles", we believe that this is so. The saint does work that miracle, but it is only through the grace of God that these people are saints, and as saints they have united themselves to Christ that they would not, nay could not, act without the blessing of God. God gives His saints the grace to work miracles, but the ultimate power is that grace from God. Saints could not be saints, could do nothing, without the power of God. That said, the saints aren't mindless zombies in heaven sent to do God's bidding. They are as you and I, people who love God and neighbor, and desire to help those in need, and they do these miracles themselves, by the grace of God.
You seem to have the very common and very erroneous belief that, for us to believe saints work miracles mean that we devalue God, that we're "stealing" glory from God. But, the Psalmist says, "God is glorified in his saints." The saints are the great cloud of witnesses, the testimony of the salvation of mankind...that though they have died, they are alive in Christ and we, as members of the Church through Christ have communion with these saints that also are in the Christ. It is the chief end of any Orthodox Christian to be what the saints are. They are our examples, not our exceptions. The same goes for the Most Holy Mother of God.