Complex sentence: In June 1897, Mother Agnes became aware of the seriousness of Thérèse's illness; she immediately asked Mother Marie de Gonzague, who had succeeded her as prioress, to allow Thérèse to write another memoir with more details of her religious life.
Split into simpler sentences: In June 1897, Mother Agnes became aware of the seriousness of Thérèse's illness. She immediately asked Mother Marie de Gonzague, who had succeeded her as prioress, to allow Thérèse to write another memoir with more details of her religious life.