The "hypostatic union" refers to the union of Christ's human and divine natures in one Divine Person. It has nothing to do with Mary, except that she helped to bring it about.
I don't know what you think "Mary sharing the 'hypostatic union' with the Trinity" means (the phrase makes no theological sense), but it's not Catholic doctrine.
p50
4 - "By becoming Mother of God, Mary belongs to the order of hypostatic union; hence SHE PARTICIPATES------>IN<-------the INFINITE SANCTITY of GOD."
p43
1 - "Hail Mary, beloved daughter of the Father, Mother of the Divine Son, Spouse of the Holy Spirit, complement of the most august Trinity!"
p46
7 - "Mary is the dawn of God because, just as the dawn marks the end of darkness and the beginning of day, so Mary indicates the end of vices and the beginning of virtue."
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[Qx: I guess Christ's conquering on The Cross and HIS conquering trip to hell were unncessary?]
9 - God loved Mary so much that He gave her the keys to His heart. 'No one can go to God without Mary drawing him.'
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[Qx: I guess Holy Spirit has been relegated to a 'Walter Mitty' role as spouse of Mary? That's SOME POWER to cancel & take over HOLY SPIRIT'S role to draw men to God!]
5 - "She desired the safety of everyone, went in search of it, and obtained it; it was also through her that this salvation was wrought."
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[QX: What an unnecessary waste of precious Blood and suffering on THE CROSS!!!/sar]
p47
10 - "As Noah's Ark saved all the animals that entered it, so Mary saves all the souls that entrust themselves to her care."
--from John Ferraro's TEN SERIES OF MEDITATIONS ON THE MYSTERIES OF THE ROSARY