“Full of grace” is literally pleres charitos and that wording is used in reference to Jesus (John 1:14) and to St. Stephen (Acts 6:8). Obviously its used with two different meanings in those two passages but its meaning is clearly gleamed by its context.
In Luke 1:28 the word that the angel uses is kecharitomene. So its not literally “full of grace” but its root word is the Greek verb “to give grace” (charitoo). The word is the past perfect tense, thus it means that the action of giving grace has already occurred. It was not something that was about to happen to her, but something that has already been accomplished. The word was used as a title for Mary, but pleres charitos is not used as a title to refer to Jesus or St. Stephen.
