Q: Do we have examples of Mary’s worthiness? I mean, why DID God choose her in the first place? What was so good about her?

There’s not a lot of information in Scripture about Mary. Her first appearance comes at the Annunciation, when the angel is announcing that she has been chosen to be the mother of the Savior. Her childhood is one of the subjects of the apocryphal text The Protoevangelium of James, which was written about 150 A.D.; in this book, Mary is described as an exceptionally holy child who goes to live in the temple at the age of three and who stays there until she is twelve. This book is not considered to be divinely inspired, so it doesn’t have the authority of Sacred Scripture, but it does show that even early on, people were interested in knowing more about the kind of person Mary was before she became the Mother of God.
We do know that God chose Mary to be the mother of the Savior. Catholics believe that she was conceived free of original sin in preparation for that important role. That said, the Church has always believed that Mary was free to reject God’s plan for her. The fact that she says “yes” so willingly seems like a clue to her values and personality. In fact, one of the women I interviewed for Mary and Me made the insightful point that Mary’s “yes” to God happens so readily that it was surely not an unusual thing for her; rather, it probably represented a lifelong pattern of openness to what God wanted for her. If that’s the case, it’s fair to say that Mary was someone who was able to put aside her own plans and wishes for the common good.