Bele Jaiande
The mother of Galehaut and Delice.
The Prose Lancelot names her land as Estregor (perhaps Estrangor?), but in the Prose Tristan, she inhabits the Castle of Tears, on the Distant Isles, with her husband Brunor.
Her husband followed a custom by which he compared a slain foe’s lady with the Beautiful Giantess and slew whichever was least beautiful. The Beautiful Giantess invariably won the contest until Tristan came to the island with Isolde. Tristan killed Brunor in combat, and then slew the Beautiful Giantess because Isolde was more beautiful.
The Italian La Tavola Ritonda gives her the proper name Bagotta (Bagota).
Sources
Lancelot do Lac | 1215-1220
Vulgate Lancelot | 1215-1230
Prose Tristan | 1230-1240