The short answer is Jesus is the New Covenant and;
Mary is the Ark of the New Covenant.
We know how revered the Ark of the Old Covenant was. It was made of the finest materials and it was holy and sacred.
The Ark of the Old Covenant held the rod of Aaron the High Priest.
Mary the Ark of the New Covenant held Jesus the Eternal High Priest.
The Ark of the Old Covenant held Manna (bread of life) for the wandering Israelites.
Mary the Ark of the New Covenant held Jesus the Bread of Eternal Life
The Ark of the Old Covenant held the the “Word of God” in stone, the 10 Commandments.
Mary the Ark of the New Covenant held Christ the living breathing Word of God in flesh.
Mary had to be pure and holy because she is the Ark of the New Covenant. The Old Testament foreshadows the New Testament.
Mary was sinless by the Grace of God.
Jesus was sinless by nature.
Email your friend the clip below, it describes Mary role supported by Scripture perfectly.
youtube.com/watch?v=kUdYeYy3NQA