Archduchess Gisela was the oldest of Empress Elisabeth's daughters to survive childhood. She had a brother, Rudolph who died at Mayerling in 1889, and a sister twelve years younger, Marie Valerie. Her Wikipedia article is here. The twelve year gap in ages between Gisela and Marie Valerie explains why Gisela is placed near the beginning of this album and Marie Valeri is placed near the end.