Mary Domenica was born on May 9, 1837, in Mornese (Alessandria).
At home she was helped to develop a solid piety, untiring work and that outstanding common sense and depth of judgement that she would show in later life as Congregational Leader.
At fifteen, she joined the Association of the Daughters of Mary Immaculate and began her apostolate among the young people of her village.
A serious attack of typhoid, at the age of 23, had a profound spiritual effect on her. The experience of her own physical fragility, on the one hand, deepened her abandonment to God and, on the other, encouraged her to open a sewing school to educate the girls in work, prayer and love of God.
Thanks to her intense sacramental life, and under the wise guidance of Fr. Pestarino, she made great progress in the spiritual life.
On the occasion of Don Bosco's visit to Mornese (10-8-1864) she said: "Don Bosco is a saint and I feel it".
In 1872 Don Bosco chose her to begin the Institute of the Daughters of Mary Help of Christians (Salesian Sisters).
As Congregational Leader, she proved a capable formator and teacher of spiritual life. She was cheerful and serene, and spread peace wherever she went. She radiated joy and involved other young people in her dedication to the education of women.
The Institute developed rapidly. At her death, she left her Daughters an educational tradition, permeated by Gospel values: the search for God, whom we come to know through enlightened catechesis and ardent love, responsibility in work, sincerity and humility, austerity of life and joyful self-giving.
She died in Nizza Monferrato on May 14, 1881.
Her remains are venerated in the Basilica of Mary Our Help in Turin.
Her feast is celebrated on May 13.