Ælfthryth

   Other names for Ælfthryth were AEflaeda, Ælfreda, Elfleda and Elfrida Countess of Flanders.

  Research Notes:

Source: familysearch.org (Kevin Bradford)

Source http://wc.rootsweb.com/cgi-bin/igm.cgi?op=GET&db=:3174654&id=I593871979 has name as Aelfreda, wife of Baldwin II (b. abt 864) and mother of Arnulf I (b. abt 889 in Flanders).

From Wikipedia - Ælfthryth, Countess of Flanders
Ælfthryth, also known as Elfrida, (died 929), was the last child of Alfred the Great , the Saxon King of England and his wife Ealhswith . She had four or five siblings, including KingEdward the Elder and Ethelfleda .
Ælfthryth married Baldwin II (d. 918), Count of Flanders . One of their descendants, Matilda of Flanders (d. 1083), would go on to marry William the Conqueror , therefore starting the Anglo-Norman line of Kings of England . Through her descendant, Henry I of England , she is also a direct ancestor of the current monarch of the United Kingdom of Great Britain and Northern Ireland , Elizabeth II .
Retrieved from ""

Ælfthryth married Baldwin II Count of Flanders, son of Baldwin I Count of Flanders and Judith Princess of France, in 884. (Baldwin II Count of Flanders was born about 864 in Flanders, Belgium and died in 918.)