Complex sentence: She was from the lesser nobility of Calabria and a nurse and governess of the future Constance of Sicily, Queen of Aragon during Constance's childhood, and followed her to Aragon upon her marriage to Peter III of Aragon in 1262.
Split into simpler sentences: She was from the lesser nobility of Calabria and a nurse and governess of the future Constance of Sicily, Queen of Aragon. Bella followed Constance to Aragon-upon her marriage to Peter III of Aragon in 1262.