False. Mary is not a Mediatrix.
There is one mediator and that is Jesus Christ.
For there is one God and one Mediator between God and men, the Man Christ Jesus, 1 Timothy 2:5
With our whole heart and with all earnestness let us venerate Mary, because such is the will of Him who has decreed that we receive everything through Mary.”
But Mary’s divine Maternity has positively made her the fountain-head of grace in its entirety.
For she presented to the world the Author of Grace, Christ, and to Him the instrument of grace, His Sacred Humanity.
If, as Bossuet argues from St. Paul, “The gifts of God are without regret”, Rom 9:29 we may safely conclude that he who started the whole work of grace through Mary will not continue or complete it without her.
This is how that celebrated preacher and theologian sums up the Catholic tradition: “God willed to give us Jesus Christ through the Blessed Virgin Mary, and since God is faithful in His gifts, this order does not change. It is and always will be true that having received the universal principle of grace through her charity, we now receive, through her mediation, its various applications in all the different states of Christian life.
Having in her maternal charity contributed to our salvation through the mystery of the Incarnation, which is the universal principle of grace, Mary will contribute eternally in all other operations of grace which are necessarily dependent upon it.”