Is there any evidence in Scripture that Mary was indeed never actually subject to original sin?

Yes. In Gen. III., 15, God said to Satan, “I will put enmities between thee and the woman … thou shalt lie in wait for her heel.” The radical enmity between Satan and that second Eve, the Mother of Christ, forbids her having been under the dominion of Satan, as she would have been had she ever contracted original sin in actual fact In Lk. I., 28, we read how the Angel was sent by God to salute Mary with the words, “Hail, full of grace.” Grace excludes sin, and had there been any sin at all in Mary she could not have been declared to be filled with grace. The Protestant version translates the phrase as “thou that hast been highly favored.” But the Greek certainly implies “completely filled with holiness.” However, complaints that our doctrine exempts Mary from the contracting of original sin are becoming more and more rare in a world which is tending to deny original sin altogether, and which wishes to exempt everybody from it.

Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty