We also believe the merit in grace is Christ's alone (Mary rejoices in God "her savior").
And I wonder if you were aware that we too hold that it is a vile, disgusting, rank heresy to say that Mary is in any way part of the Godhead. Any Catholis that so says should be anathematized posthaste.
BUT...our Lady enjoys a relationship with the Godhead that no-one ever did before or since. She is the daughter of God the Father, the mother of God the Son, and the spouse of the Holy Spirit. I would respectfully ask you to consider whether the current level of respect you have for her would be sufficient for someone who was literally impregnated with God.