Born in Gracchiano-Vecchio, Tuscany, Italy, in 1268, by the age of six, she was already begging her parents to enter the convent. By nine she was allowed to enter and at fifteen "to the distress of young Agnes, she was elected abbess. Since she was only 15, a special dispensation was needed--and provided by Pope Nicholas IV." From here:
During this time Agnes reached a high degree of contemplative prayer and was favored with many visions. One of the loveliest is the one for which her legend is best known: the occasion of a visit from the Blessed Virgin. Our Lady came with the Holy Infant in her arms, and allowed Agnes to hold Him and caress Him. Unwilling to let Him go, Agnes hung on when Our Lady reached to take Him back. When she awakened from the ecstasy, Our Lady and her Holy Child were gone, but Agnes was still clutching tightly the little gold cross He had worn on a chain about His neck. She kept it as a precious treasure.
Agnes returned to Montepulciano to die in the night. When she knew she was dying after a long and painful illness, Agnes told her grieving nuns that they should rejoice, for, she said, "You will discover that I have not abandoned you. You will possess me for ever." The children of the city wakened and cried out, "Holy Sister Agnes is dead!" She was buried in Montepulciano, where her tomb soon became a place of pilgrimage.
One of the most famous pilgrims to visit her tomb was Saint Catherine of Siena, who went to venerate the saint and also, probably, to visit her niece, Eugenia, who was a nun in the convent there. As she bent over the body of Saint Agnes to kiss the foot, she was amazed to see Agnes raise her foot so that Catherine did not have to stoop so far!