St. Louis de Montfort describes how prayers to Mary are transferred to God

When Catholics pray to the Blessed Virgin Mary, it is not due to an act of worship, because worship is given to God only.
An 18th-century priest, known as Louis de Montfort, a good devotee to the Virgin Mary, explains what happens when prayers are addressed to Our Lady.
The explanation is found in one of his book titled, True Devotion to Mary. He kicks off by saying that a very sincere and devout prayers to the Virgin Mary “will give more glory to Jesus in a month than in many years of a more demanding devotion.”
Louis de Montfort explains that Mary is a pure conduit for our prayers, who transforms them into glorious prayers to her Heavenly Father.
In so many ways, Mary is an echo of God, speaking and repeating only God. So, whenever you say “Mary” she says “God.” Even when St. Elizabeth praised Mary by calling her blessed because she had believed, Mary, as the faithful echo of God, as she responded with her canticle, “My soul glorifies the Lord.”
Whatever Mary did on that day, she does every day. Whenever we praise her, love and honour her, whenever we present anything to her, then Our Lord is praised, honoured and loved and receives our gift through Mary and in Mary.
Remember that whenever you say “Mary” she says “God.”
In another instance, Montfort imagined the Virgin Mary taking our prayers in her hands and transforming them when presenting them to God.
Our Blessed Lady, in her deep love for us, is ready to receive into her virginal hands the gift of our actions, communicating to them a marvelous beauty and splendour, and also presenting them herself most willingly to Jesus.
More glory is given to our Lord in this way more than when we make our offering with our own filthy hands.
Any time you offer prayers to the Virgin Mary, do not forget how she receives your prayers and takes them to God directly. In reality, the closer we are to Mary, that’s the closer we are to God.