Daughter of Sir Guengasoain.
Gawain killed her father to avenge the death of Sir Raguidel, and he therefore had the right to marry Trevilonete. Gawain saw that she was in love with Yder, and relinquished his claim, allowing Yder and Trevilonete to marry.
Source
La Vengeance Raguidel | Raoul, possibly Raoul de Houdenc, early 13th century