Her labors were dedicated instead to consolidating a new religious congregation which began to grow after World War II until Mastena's sudden death in 1951.

[1] Mastena later asked to enter the religious life in 1895 as a teenager but was accepted as a postulant much later on 3 September 1901 at the Institute of the Sisters of Mercy of Verona.

To that end she left the congregation and on 15 April 1927 entered the Cistercian convent San Giacomo di Veglia in Vittorio Veneto where she assumed the religious name Maria Pia.

[2][3][4] On 15 November 1927 the Bishop of Vittorio Veneto, Eugenio Beccegato, her spiritual director, asked her to leave the convent and resume teaching after Mastena had doubts as to whether the contemplative life was meant for her.

In San Fior in 1930 she organized a small community called "Pious Rescue" which was aimed at assisting poor children and teaching them a trade.

[2][4] Towards the middle of the 1940s the congregation began establishing small offices in other Italian cities and on 12 May 1940 Mastena met Pope Pius XII in a private audience to discuss her work.

[1] This was during World War II and the congregation participated in relief activities for soldiers and victims of the conflict and fed them free of charge and without distinction between Italians or Germans or Jews since no side existed in their view.

[3] The beatification process opened on 23 June 1990 after the Congregation for the Causes of Saints issued the nihil obstat ("no objections") and titled Mastena as a Servant of God.

The theologians tasked to assess the cause approved the dossier's contents on 17 March 2002 while the cardinal and bishop members comprising the Congregation agreed with this decision at their meeting on 7 May 2002.

Pope John Paul II confirmed that Mastena had lived a model life of heroic virtue and named the as venerable on 5 July 2002.

[5] Benedict XVI stated in his remarks following the beatification Mass: She was beatified thanks to a miracle recognized by the Catholic Church to the daughter of Sandra Milo, Azzurra, who seemed dead at birth, but came back to life.