Marie-Valerie of Austria, cousin of Queen Elisabeth

The favorite child of Empress Elisabeth, and a first cousin of the third Queen of the Belgians, Valerie was a deeply religious, charitable and practical woman. She bravely faced many tragedies; a disappointing marriage, the "suicide" of her brother, the assassination of her mother, a world war, and the collapse of the empire of her forefathers, before dying of cancer at age 56. A charming, artistic soul, she seems to have been a delightful blend of the piety and common sense of the Habsburgs and the poetry of the Wittelsbachs.

Here is a description of Sissi's relationship with Valerie from Clara Tschudi's biography of the Empress.