"If Miriam was born without the stain of Original Sin, she did not need a Messiah."
Baloney. Sinless or not, Mary needed a Messiah just as much as anyone else, because without the grace of God, no one can avoid sin.
Not sure which part of this article you don't understand, much less the Bible. Mary is the Mother of God. God chose her ... He had a plan. He intended her to bear our Savior. If nothing else, simple common sense would tell you that God, who is perfect, would choose to enter this world through a perfect vessel. Without Mary's "yes", there would be NO salvation.
Is this any clearer to you? Do you realize that your comments about His mother actually insult Jesus? If you love Him, as you seem to indicate, then why would you insult Him in this manner?