Whether she sinned or not, has no bearing on God’s plan for salvation. None. God does what He wants, using us despite our shortcomings.
A recurring theme in protestant responses seems to be “What does that have to do with Salvation?”. I take issue with this. It cannot be about us as individuals. I think the single mindedness of our own Salvation rather than the total understanding and pursuit of the Truth of God’s plan and ‘Who God is’ is the problem.
We NEED to be sure we are participating in our own Salvation, of course (i.e., Baptism, Penance, etc.), but we also have a duty to make sure we understand what God wants us to know - this is a part of our Salvation, for if we don’t know Him, then we don’t know what we are supposed to do to participate in that Salvation.
The importance of accepting the truth of Mary’s role and position speaks to who Christ was. It is a part of our understanding of Him (reaching back to the OT - Christ the New Convenant, 10 Commandments the old, Mary new Ark, Old Ark is Old Ark of the Old Covenant). God chose her to have his humble servant, Mary, to bear Himself (2nd Person). This is a part of our understanding of Jesus, and who He was, since she played such an intricate role. If we disregard her, or any of the saints, we lose our understand of Him in a certain regard.
If I want to understand physics, don’t I HAVE to read the writings of Hawking, Einstein, and the rest? Can I understand physics without them?
Physics is just a material concept. God is the creator of those laws. What does it take to understand God? We must read about those who have lived the Way that Christ said to. We must also understand them and how they applied His teachings. If not, we don’t fully know Christ.
Back to my original thought … Let us not just be concerned with our own Salvation, but rather, our Salvation AND true understanding of God. Our understanding assists us on staying true to the path of our Salvation.
My rule: If you respect and honor anyone in this life, honor Christ first, then Mary, then saints, then everyone else. Who else is going to show you, by their example, the way to worship God? I’ll be keeping Mary as my spiritual mother, and the saints as my mentors. They all show me how to love Christ, because they did it more than I could ever hope to.