She Who Was Nothing
I love the fact that she was a lay woman, not a religious sister or nun. She was in the exact state of life she needed to be to do the work God gave her. If she were a nun or sister she would have been under obedience to a superior and that would have been the end of her mission, for sure.
As I mentioned, she was unschooled. Hence, the fact that she conversed with political figures and princes, in the warring Italian cities, is proof that God was with her. Why else did anybody pay her any mind, were He not?
She is famous for telling the pope where to go. Pope Urban VI moved the papacy to Avignon, France. Catherine convinced him for the good of the church to move back to Rome. The papacy never left Rome again.
How could an unschooled girl have this power over political and religious leaders, were she not from God? And she did it by identifying her will with God's. This shows that strength comes from accepting God will and one's nothingness.
Catherine worked among the sick and in her era pestilence thrived. She had an affinity for society's poor souls. She labored in prisons and befriended the condemned, including catching the head of a condemned guillotined man.
She performed miracles and even received the stigmata. Upon requesting that the overt display of the wounds be taken away, but not the pain, her request was granted. She didn't want to "show off" in any way, not that the gift of stigmata wasn't wanted.
She changed her world. "If you are what you are meant to be, you will change the world."
Because of her humility, charity, prayer and sacrifice, she was made a Doctor of the Church.