No, it's not. I am "full of turkey" after Christmas dinner. But I still have room for apple pie.
All true believers in Jesus Christ are "full of grace."
And yet we still sin because we are human and not God.
Mary's soul was filled with Grace. The Soul has the attributes of will and intellect. Filled as it was with Grace it was not susceptible to concupisence and failure/errors in the application of will or intellect.
That'ss just my off-the-top-of-my-head explanation. I'lll post a link in a second