After successfully completing the three-year program, she continued her studies at the School of Domestic Science, also directed by the Servants of Charity.

She requested from him the Rule of the Third Order Franciscans, and, in the winter of 1919, opened three institutions in Blato: a day-recovery centre, a child-care facility, and an orphanage.

On that day, Petković received the name of Marija od Propetoga Isusa (Mary of Jesus Crucified) and was chosen as the Mother Superior of the Order.

[2] In addition to catechesis, she organized instruction in hygiene, economics, homemaking, sewing and tailoring, knitting, nursing, and typing.

In 1961, she concluded that her duty to the Congregation was no longer one of leadership but of sacrifice and suffering, prayer and offering herself to the Lord, and relinquished the office of Mother Superior that she had held for 40 years.

She continued to follow the events in the Catholic Church and her Congregation, especially those changes brought about by the Second Vatican Council, until age 74, when she died.

On 8 May 1998, Pope John Paul II confirmed the Congregation's initial report and decreed that Petković's heroic virtues be publicly declared, formally recognizing her as "Venerable."

On 6 June 2003, Pope John Paul II celebrated her beatification Mass in Dubrovnik, formally recognizing her as "Blessed."

Today, her Congregation has its branches, besides other countries, in Italy, Romania (by Greek Catholic community), Paraguay, Chile, Peru and Argentina.