As the abbey announced on Friday, the 21 members of the convent elected Hartwig as interim superior.
She now has the task of preparing the election of a new superior.
The previous abbess, Hildegard Dubnick, who comes from the USA, resigned from office on 24 March after a good five years.
Cultural differences had been the deciding factor.
After taking a break in another monastery, she plans to return to the United States this year, it was reported.
At the abbey since 1990
According to the press release, Sister Elisabeth Hartwig comes from Torgau and initially studied physics in Jena.
She joined Sankt Walburg Abbey in 1990. She currently works as a religion teacher at a primary school.
She is also trained in spiritual counselling.
The Benedictine abbey of Sankt Walburg is historically significant in two respects.
Firstly, it guards the tomb of St Walburga, the patron saint of the Eichstätt diocese (presumably 710-779).
Secondly, Benedictine nuns have lived here continuously since it was founded in 1035.
This constant presence has preserved many art treasures and archives on site.