The blessed Virgin was conceived immaculately free from Original Sin by the application of the merits of Christ’s’ Redemption preventively (instead of healing for the rest of mankind). Lk 1:28: “Hail full of grace.” This indicates a perfection of grace. This perfection is thus intensive and extensive – over the whole of her life from conception.
“Full of grace” is a unique title given to Mary, and suggests a perfection of grace from a past event. Mary is not just “highly favored.” She has been perfected in grace by God. “Full of grace” is only used to describe one other person - Jesus Christ in John 1:14.
Karl Keating remarks that these newer translations, based on the Greek, "are imperfect since they give the impression that the favour bestowed on Mary was no different from that given other women in the Bible…indistinguishable from the status of Elizabeth, the mother of John the Baptist; or Sarah, the wife of Abraham; or Anna, the mother of Samuel * all of whom, by the way, were long childless and were ‘highly favoured’ because God acceded to their pleas to bear children.”
Karl Keating says that the older translations convey that this grace is permanent and of a singular kind in keeping with the Greek which indicates a perfection of grace, and which is what the dogma of the Immaculate Conception teaches. He stresses that the sense of the Greek kecharitomene is not just “to look upon with favour, but to transform by this favour or grace.” (From René Laurentin).
Convert from Evangelicalism, ex-Pastor David B Currie, in his book* Born Fundamentalist, Born Again Catholic* thinks that St Jerome “probably did the best job of translating this passage so many centuries ago. He translated it as ‘Hail, full of grace’. The important point to notice is that Mary is not addressed by Gabriel as ‘Mary’. She is addressed as ‘full of grace’, as though that were her name. When we unpack the Greek meaning of these words, Gabriel called Mary ‘The One Most Full of God’s Gracious Gift of His Life in All Time’.”