If Mary is sinless then how is Christ her victory?

Catholics and the Eastern Orthodox church believe in the sinlessness of Mary. Although their beliefs differ, they agree on the belief that "Mary was sinless." If Mary is sinless (i.e. the Catholic belief that Mary was created without the stain of original sin, and also did not sin. OR - the Eastern Orthodox belief that denies original sin, yet claims Mary never sinned) how, then, is Christ Mary's victory? Christ's sinless life, death, and resurrection is our victory. He is our perfect example. He is the only One who perfectly loved God with all of His mind, soul, heart, and strength. If we say that Mary is *also* in the sinless category - how is this not robbing Christ of His Glory? Additionally, how is this not demonstrating that Mary *cannot* say "Christ is HER victory?" If the doctrine of the sinlessness of Mary is true, she cannot rely on the sinless life of her Son. She cannot fall on her knees in humble gratitude to her Son, accepting His perfect life, because she would have done it without Christ. Thoughts on how the doctrine of the sinlessness of Mary does not do the following: (1) robs Christ of His unique office and glory (2) robs Mary of the opportunity to fall in humble gratitude to her Son's perfect life. (3) cause us to turn our eyes on Mary *also* (which consequently robs Jesus of the focus)