On the contrary, it is definitive proof of the sinful state of the person on whom it was given.
If Mary had not sinned, she COULD NOT HAVE experienced God's grace. Grace is not needed without sin.
It's only in the presence of sin where grace kicks in.
Where sin abounds, grace much more abounds.
Romans 5:20 Now the law came in to increase the trespass, but where sin increased, grace abounded all the more,
It appears that having lots of Grace like Mary means there must have been lots of sin!
Oops!
It does in the Catholic world-view when talking about the "infusion" of grace versus the "imputation" of righteousness. It's the soul gas tank example I gave a number of days ago. Gotta keep that tank on FULL in order to make it to heaven. Mortal sins empty the tank like it sprang a leak and only confession and penance WITH good works can bring it back to nearly full (seeing as RCs believe most people will have to go through Purgatory first to top off the tank). I can't understand why it doesn't register that we are saved because of CHRIST'S righteousness and not our own - which IS the Biblical view.