She grew in piety and eventually became a Benedictine Nun. She was elected Abbess at a young age after her Superior died. Although her parents founded the Monastery, she felt God chose her calling to become a Nun. Her holiness and reputation spread, and when she was twenty eight, the Bishop of Augsburg appointed her Abbess of Edelstetten and told her to reform the Convent. Despite her protests that she was not old enough for the task and could be unable to cope with the problems of the Convent, she accepted the appointment.
She received instructions from Pope Anastasius IV about the reform that he desired. She received a warm welcome at first, but soon into her new position she was met with a great deal of resistance. When she began to enforce discipline, they were not cooperative with her. The measures that she took were that the Nuns start observing the Benedictine Rule, that the enclosure of the Convent be followed, especially the rule denying admission to visitors who came to spread gossip. She was only able to succeed after the Bishop expelled the main troublemakers. Soon she won over the other Sisters. In addition to her reputation for holiness, she had strong administration skills. She became well know for her miracles of healing, restoring speech and vision, and her mystical trances and ecstasies that would often last for hours. She was considered a model of Religious life. Shortly before her death in 1160,
St. Mechtildis resigned as Abbess and returned to Diessen, where she died on May 31. Her life is an example that reminds us, whether we are Religious, Married or Single, we are all called to enter into the holiness and love of God, and to be of service to others.