Didn't Mary, mother of Jesus have to be sinless and perfect in order to be chosen as Holy Mary?

It would seem that there would be a certain level of purity and sinlessness to be chosen as the "Holy Mother" in the first place. (I mean, let's face it, it must have been a tough story to sell) I don't doubt her sinlessness and yes, I have gone to her hundreds of times for help and influence with her son. And I am always in awe of her greatness and holiness. I do know she has answered me with only the gentleness of the mother of the most High. I am curious to know how others perceive Mary. Imagine the strenght and resolve she had to have to see her son crucified. What are your feeling?