She was a nun (Wiliamson, David. Debrett's kings and queens of Britain. Topsfield, Mass. : Salem House Publishers, 1986, pg. 43).

Adeliza or Adelida (died before 1113) was a daughter of King William the Conqueror and his wife, Queen Matilda of Flanders. There is considerable uncertainty about her life, including her dates of birth and death. In a mortuary roll prepared at her sister's religious house, she was listed first among the daughters of William the Conqueror. She was usually the first daughter in lists of William's children, and thus probably the eldest. Her inclusion in the mortuary roll indicates that her death preceded the date of its 1113 compilation (wikipedia)