Nothing that the Catholic church claims it means is anywhere supported in Scripture.
FWIW, ALL believers are grace d with the same grace that Mary was given.
Mary and Grace
The word grace used in this passage in Luke is used in one other place in the Bible and that is Ephesians 1 where Paul tells us that with this same grace, God has blessed us (believers) in the Beloved. IOW, we all have access to that grace and it has been bestowed on us all.
http://biblehub.com/greek/5487.htm
Luke 1:28 And he came to her and said, "Greetings, O favored one, the Lord is with you!"
Ephesians 1:4-6 In love he predestined us for adoption as sons through Jesus Christ, according to the purpose of his will, to the praise of his glorious grace, with which he has blessed us in the Beloved.
Greek word "grace"
charitoo: to make graceful, endow with grace
Part of Speech: Verb
Transliteration: charitoo
Phonetic Spelling: (khar-ee-to'-o)
Short Definition: I favor, bestow freely on
Definition: I favor, bestow freely on.
HELPS Word-studies
Cognate: 5487 xaritoo (from 5486 /xarisma, "grace," see there) - properly, highly-favored because receptive to God's grace. 5487 (xaritoo) is used twice in the NT (Lk 1:28 and Eph 1:6), both times of God extending Himself to freely bestow grace (favor).
Word Origin: from charis
Definition: to make graceful, endow with grace
NASB Translation: favored (1), freely bestowed (1).
The Good Doctor explains it in Luke 1:30. He says she's found favor with God because she's been chosen by God to give birth to Christ.
The context of the passage answers the bulk of the questions catholics seem to keep missing.
Yea that’s nice, but it still says she was full of grace. Sorry.