A maidservant of Queen Amena of Korntin (Amene) in Wirnt von Grafenberg’s Wigalois.
She traveled to Arthur’s court to find a champion when Korntin was invaded by King Roaz of Glois. When Arthur appointed Wigalois (Gawain’s son) to the task, Nereja was furious because she thought Wigalois too young and inexperienced.
As she traveled with Wigalois, however, and watched him win a number of combats, she gradually developed respect for and confidence in him. By the time they reached Roimunt (Amena’s castle), Nereja was happy to present Wigalois as her champion.
Her counterpart in Renaut de Bâgé’s Le Bel Inconnu is Helie.
Source
Wigalois | Wirnt von Grafenberg, early 13th century