In the Bible, it says that Mary is full of grace. The Greek word for this is only used once..it means she is literally full of grace, there isn't anything else, there's no sin in her. She was saved by God too, like all people, but at her conception...
You are correct that
FORM of the greek word is used only once but the root word is still grace.
http://www.scripture4all.org/
Luke 1:28 And the messenger entering towards her said "be thou rejoicing! having been favored/graced/
kecaritwmenh <5487> (5772). the Lord with thee............
Textus Rec.) Luke 1:28 kai eiselqwn o aggeloV proV authn eipen caire
kecaritwmenh o kurioV meta sou euloghmenh su en gunaixin
W-H ) Luke 1:28 kai eiselqwn proV authn eipen caire kecaritwmenh o kurioV meta sou
5487.
charitoo khar-ee-to'-o from 5485; to grace, i.e. indue with special honor:--make accepted, be highly
favoured.
5485. charis khar'-ece from 5463; graciousness (as gratifying), of manner or act (abstract or concrete; literal, figurative or spiritual; especially the divine influence upon the heart, and its reflection in the life; including gratitude):--acceptable, benefit, favour, gift, grace(- ious), joy, liberality, pleasure, thank(-s, -worthy