... it is still often argued that she must have been a sinner because "all have sinned" (Rom 3:23). But if we press St. Paul into rigorously meaning by this "every last human being on earth, especially Mary" there is no way to keep that steam roller from running over Jesus too, since Paul does not say "all have sinned except for Jesus." Perhaps looking at the whole thought would be helpful. There is a clear exception. Rom. 3:23-24 -
"...23 for all have sinned and fall short of the glory of God, 24 and are justified freely by his grace through the redemption that came by Christ Jesus."
Paul gives the reader credit for knowing that Jesus did not need to redeem himself.