“...no biblical basis...”
The fact that Mary is full of grace is in the bible. Jesus required an immaculate (sinless) vessel for his Divine Nature. Mary required a savior - she was “saved” in advance so her vessel was pure - she is prefigured by the ark of the covenant in the OT.
The state of being full of grace = having been saved.
That is ridiculous on its face. Jesus is the only sinless one born (technically Adam and Eve weren't born) to claim otherwise is to deny that all have sinned
(Romans 3:23) — so you are obviously rejecting scriptural truth & authority [of Romans] by claiming Mary is without sin, are you not?
The physical body (one’s members/the flesh) is not made sinless the moment one receives God’s gift of salvation through Christ. The believer is still capable of sin. Sin is the result of the “old nature” and those sins come about by the actions of the flesh (the physical/mental/emotional state of the believer). Paul, in Romans 7 bewails this fact, “Who can deliver me from the body of this death?”
The one who accepts Christ as Savior is delivered from the penalty of sin (”There is, therefore, no condemnation to them that believe...”, from the power of sin (it can no longer render the believer [eternally] dead), but we are not delivered from the presence of sin (our full salvation) until the day we are “ever with the Lord” in eternity.
Christ, and Christ alone, is the only One ever referred to in Scripture as being “full of grace [and truth]” - John 1:14.
No, He didn't. And besides, that would be HIS body, not hers.
God's Holy Spirit lives in believers, who sin.