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

Haylan is Milderd's sister-in-law. Haylan turns down Wulfgar's advances when he calls Aislinn's name. Upon learning that Aislinn is only Wulfgar's mistress, Haylan sets her sights on him and vows to win his heart, spurred on by Gwyneth who would like to see anyone unseat Aislinn. Haylan apologizes to Aislinn when Aislinn saves the life of Miles, Haylan's young son.