Adam and Eve were created without sin.
It is our free will that allows us to sin.
It is God’s grace that aids us in resisting temptation.
Mary was “full of grace” meaning she had all the graces she needed to lead a sinless life at the behest of God who chose her to bear His only Son.
She did not merit this on her own.
She had need of Jesus as Savior as we all do.
You appear to be dancing around with your words. If, as Catholics claim, Mary was sinless for whatever reason then Jesus was not the only sinless human. That’s blasphemy.