Saint Agnes of Montepulciano

During one of Catherine of Siena's ecstasies, she exclaimed, referring to St. Agnes of Montepulciano: "I give you thanks oh my Lord, for showing me the place that will be mine (in Paradise), next to my sister Agnes."
Who is this Saint (virtually unknown in our country) that a powerful Saint and Doctor of the Church - Catherine of Siena should say this of her?
We're about Holy Clusters again. God is bringing us to Tuscany, once more, ancient Tuscany filled with a history of the greatest Saints and most deplorable sinners. Agnes, one of the great Saints was born in 1268, in a hamlet three miles from Montepulciano, named Gracciano, in the "Villa di Gracciano Vecchio." A Dominican like Catherine, Agnes would die April 20, 1317, thirty years before Catherine of Siena was born. Again, the Church is in crisis; again God sends us powerful men and women Saints!
Agnes was born into the nobility. At age nine, she would ask permission from her parents to enter a monastery of Nuns living a very austere life, in Montepulciano. They were called Le Suore del Sacco, Sacchine or Sisters of the Sackcloth, because of the coarse material of which their habits were made.