According to Bede, in 695, Seaxburh organised the movement (or translation) of Æthelthryth's remains to a marble sarcophagus, after they had lain for sixteen years in a common grave.

The legend is described in Bede's Ecclesiastical History of the English People, which celebrates the saintly virtues of Æthelthryth, but speaks less highly of Seaxburh, referring only to her marriage, succession as abbess and translation of her sister's relics.

In the same passage is the Chronicle's single reference to Seaxburh and Eorcengota, "...þaes dohter wæs ge haten Erchongata halifemne.

According to Barbara Yorke, Seaxburh's marriage was itself of seminal importance in the establishment of monastic life for women during the Anglo-Saxon period, as she became an example of an ex-queen who made retreating to an nunnery a desirable royal vocation.

[note 1] According to the Liber Eliensis, a 12th-century chronicle and history written at Ely, an English source related that Seaxburh received "the veil of holiness" from Theodore, the Archbishop of Canterbury, in her church on the Isle of Sheppey and that her daughter Eormenhild also became a nun there.

[12] Seaxburh is said by her hagiographer to have sought refuge as a nun after living a secular role that she had found hard to tolerate: having reluctantly submitted to marriage, she hastened from queenhood to "a timely widowhood and a hasty withdrawal to the religious life", according to Susan Ridyard.

According to Yorke, Seaxburh's retirement to Ely is an example an Anglo-Saxon custom represented in a law: whereby a married woman remained the responsibility of the paternal side of her family, perhaps to spend the rest of her days as a nun or an abbess.

[16] Seaxburh's previous political experience in East Anglia and Kent would have been useful in preparing her for the role of abbess at the double monastery at Ely.

[22] She apparently oversaw the translation of her sister's remains without the supervision of her bishop, using her knowledge of procedures gained from her family's links with the abbey at Faremoutiers as a basis for the ceremony.

[23] The fourth book of the Ecclesiastical History of the English People, completed by the Northumbrian monk Bede in 731, celebrates the monastery at Ely and focuses on Æthelthryth's piety and the translation of her relics.

[28] Seaxburh is mentioned in a written account of Kent's earliest Christian kings and their canonised relatives, known as the Kentish Royal Legend (Old English: Þá hálgan).

The Life (or Vita) printed in John Capgrave's Nova, Legenda and used by the Bollandists, was perhaps copied from a Cotton manuscript in the British Museum.

The Vita describes Seaxburh's early life, marriage to Eorcenberht, withdrawal to Milton and then Minster-in-Sheppey, and her final years as a nun and the abbess at Ely.