Teresina Mainetti was born to a small Lombard fisherman's family at Colico on Lake Como. She entered the Daughters of the Cross at fourteen in 1953, taking the religious name Maria Laura. After completing teacher training she served the order's school ministry at Vasto, Rome, and Parma across the 1960s and 1970s. From 1984 she served at the Daughters of the Cross house at Chiavenna in the high Lombard Valtellina — as catechist, teacher of religion at the local middle school, and director of the parish youth oratory.
Three teenage girls of the Chiavenna parish youth group — aged 16, 16, and 17 — had become involved with an underground satanic-ritual subculture in Sondrio Province in late 1999. The three formed a plan to perform a 'ritual sacrifice' as an entry into the satanic group. They selected Sister Maria Laura specifically because she would trust them (she had personally counselled all three). On the night of June 6, 2000, the three girls — under pretext of a religious-vocational conversation — lured the sixty-year-old Sister Maria Laura to a small wooded park in central Chiavenna. They struck her on the head with rocks, then stabbed her nineteen times with a kitchen knife.
According to the girls' subsequent confessions in court, Sister Maria Laura — fully aware of what was happening — repeatedly prayed aloud for them as they were attacking her, ending with the words 'Lord, forgive them' (Signore, perdona loro). The three girls were tried as minors and convicted in 2001; all three made public statements acknowledging their guilt and (two of the three by 2014) had returned to Catholic practice. Beatified June 6, 2021 — exactly twenty-one years after her death — by Pope Francis through delegate Cardinal Semeraro at Chiavenna. The beatification was officially decreed as martyrdom in odium fidei.