Who is Gwyneth from The Wolf and the Dove and what is their importance?

Gwyneth is Wulfgar's half-sister. Gwyneth is bitter, hates everyone and makes life miserable for all those at Darkenwald. When Wulfgar leaves the hall, Gwyneth rules with an iron fist, hating Aislinn all the more when servants and others seek her out over Gwyneth or ask Aislinn whether to follow Gwyneth's orders. Gwyneth carries the secret that their mother lied when she said that Wulfgar was not Bolsgar's son, and that it's actually Gwyneth and the other brother who do not belong to Bolsgar. She dies at the hands of Ragnor, who she believes she loves and begs Aislinn's and Wulfgar's forgiveness just before she dies.