So Mary was "just chosen", eh? All the same, the fact remains that G_d chose Mary over anyone else means that He considered her most worthwhile. Who's going to argue with G_d Himself?
I am a Born-Again, (now a Presby with a new respect for the Catholic faith, thank you blessed John Paul the Great) but one willing to respect the Blessed Virgin Mary. It may be that G_d alone answers prayers, but He choses the saints to help listen and carry out, kind of a heavenly conduit.