She was abbess of Whitby Abbey, an abbey of nuns that were known for their skills in medicine, from the death of her kinswoman Hilda in 680, first jointly with her mother, then alone. When she was about a year old, her father, King Oswiu of Northumbria, in thanksgiving for his victory over Penda of Mercia at the Battle of the Winwæd, handed her over to abbess Hilda to be brought up at Hartlepool Abbey.
Ælfflæd was particularly known for her skills in surgery and her personal attention to patients, as was Hilda, who was known for her personalized medical care. Most of Ælfflæd"s life was spent as a nun. When Hilda left to found Whitby Abbey in 657 or 658, she brought Ælfflæd with her.
The Northumbrian church of Cuthbert"s time, was a wealthy and aristocratic institution.
On at least one occasion princess Abbess Ælfflæd is found banqueting with Saint Cuthbert of Lindisfarne. In the of Saint Cuthbert, the saint assures Ælfflæd who is concerned over the succession, that she will find Ecgfrith"s successor "to be a brother no less than the other one" (Anon V Cuthberti 36).
Cuthbert then tells the puzzled Ælfflæd that this brother is "on some island beyond this sea", at which point she realises that he is talking of Aldfrith "who was then on the island which is called Iona" (Anon V Cuthberti 36). According to one account, Ælfflaed had been afflicted with a crippling disease for some time.
One day she thought about Cuthbert and wished she had something belonging to him, for she was certain that would help her.
Soon afterwards a messenger arrived with the gift of a linen girdle from Cuthbert. She put this on and within three days was restored to health. Her piety was praised by contemporaries such as Bede and Eddius.
Bede refers to her high degree of holiness and devotion, while Eddius calls her the consoler of the whole kingdom and the best counsellor.
Ælfflæd was considered a saint and her feast day was celebrated on 8 February. She was buried at Whitby.
A late hagiography, the Vita sanctae Elfledae, survives, collected in John Capgrave"s Nova Legenda Angliae of 1516. Excavations in the 1920s by Radford and Peers found several building foundations and two inscribed memorial stones believed to record the deaths of Saint Ælfflaed, Abbess of Whitby, and Cyneburgh, queen of King Oswald.
