Is Mary Greater than Christ?
Since Mary is the queen of all created reality, is she greater than Christ's created human nature?
No. Mary is queen of heaven and earth—or, as you put it, "of all created reality"—only in relation to her Son, who is King of kings and Lord of lords. Her queenship derives from her status as Mother of the King, not as something she inherently possesses.
An analogy might be drawn to human kingship. The wife and mother of a king is given the title and respect owed to a queen by virtue of her marriage and motherhood. A modern example of this would be the late queen consort, Queen Elizabeth of England, who was queen by virtue of her marriage to King George VI. After his death, she became known as the "Queen Mother" to distinguish her from her daughter, Queen Elizabeth II (who is Queen of England by right of inheriting the throne from her father).
The Blessed Mother is queen of heaven and earth only because she is the Mother of the divine King, God the Son.