The fact that Mary was conceived without Original Sin means that she had the fullness of free will. Mary did not suffer from disordered desires, disharmony with God, subject to ignorance nor have an inclination to sin. Original sin weakens our free will (but does not destroy it), Mary’s free will was not weakened. All of us who suffer from the effects of Original Sin do not make good choices because of our weaknesses, disordered desires, etc. In a certain sense Mary made the freest choice humanly possible because she was able to see, understand and desire goodness/holiness without impediment.
