The tract in the pre-1970 Mass of the Common of the Blessed Virgin begins: “Rejoice, O Virgin Mary, thou alone hast destroyed all heresies. Who didst believe the words of the Archangel Gabriel.”
Why is Our Lady the destroyer—or Exterminatrix—of all heresies? Because she believed the words of the Archangel Gabriel; her fiat of absolute faith in God is enough to overturn every heretical un-belief the rest of us can concoct. She allowed the quintessentially authoritative Word of God to inhabit her completely, body and soul, something no erroneous word could ever withstand.
Intellectually, it is a lovely idea, but does our experience bear this out? Yes. Throughout history, Our Lady has been a stumbling block to heretics and a nurturing mother to the truth.