Dear Stephen:

St. Stephen's "full of grace" was an existential event, that is, he was, as we can be, filled completely with the Holy Spirit at the time he performed his wonders. Acts 6:8 states: "Now Stephen, filled with grace and power, was working great wonders and signs among the people." The Scripture gives no indication that this state of fullness was permanent. The phrase "full of grace" is an adjective phrase, it describes Stephen at the moment.

We too can be full of grace at particular times. We do not, however, maintain that fullness for long. The amount of grace we have within us various depending on our level of union with Christ at any given moment.

The Blessed Mother, on the other hand, was full of grace ontologically, that is, she was in a permanent state of grace that was complete and full at all times. That privilege was granted to her by her Immaculate Conception and allowed her to remain sinless all of her life. In Luke 1:28 the phrase "full of grace" is given by the angel as if that was part of her name not just describing her spiritual condition. It was, as it were a noun phrase.

I would like to provide a better answer, but we have just moved St. Michael House to Iowa just a couple of days ago. Most everything, including some books I wanted to check for this question, are buried in a box somewhere. The above answer is my sense and understanding of this -- at least from the top of my pointed head.

God Bless,
Bro. Ignatius Mary