This works out in Luke 1:28 very straightforwardly. Mary received a great kindness from God. She received it at some point in the past, and she is still benefiting from it in the present. Done. Then we learn what that great kindness was, that she should be chosen to give birth to the Messiah. That's the grace/kindness/favor she received, and she received it gladly.
Mrs D, really, one of the reasons it would be good for you to source that whole misconstruction of the Greek you cited is to evaluate the source, and perhaps see if a response has been posted to refute it. I tried going back and finding it, but couldn't find the original citation. I'm thinking whoever posted it probably removed it because it is so utterly indefensible. That's not your fault. But it's kind of a peer review thing.
BTW, there is a simple, grammatical reason for the passive being used in Luke 1:28 and the active in Ephesians 1:6. In Luke 1:28, God is presumed to be the giver of the kindness to Mary, but in Ephesians 1:6, God is explicitly set out as giver of this grace/favor/kindness to us. So in Luke 1:28, the subject being unnamed (God) transfers the focus of the verb to the object (Mary) the passive recipient, but in Eph. 1:6, the subject has been named (verse 1, God), so the verb takes on the active voice, even though the object ("us") is just as much a passive recipient of the grace/favor/kindness as Mary.
Bottom line, no creditable Greek scholar would find any real difference between Ephesians 1:6 and Luke 1:28, based simply on person, number, or voice. Those are structural requirements for each context, but they don't change the meaning at all. They are both based on charitoo, both in the perfect tense, both describe recipients of an action, that action is done, but has ongoing consequences. Therefore, if you make a special pleading for Luke 1:28, it necessarily applies equally to Ephesians 1:6. If you can stretch the "perfect" to give Mary "full grace," then every Ephesians 1:6 believer necessarily has the same thing. Same subject, same verb, same tense, same effect. Much better to just let the text inform us that both we and Mary have been shown great and undeserved kindness by our God, and that the blessings from that favor just keep on coming.
Peace,
SR
I know that Mrs. D is truly sincere but has been misled and really needs to do some independent study.