Who is Blanche d' Artois from The Reckoning and what is their importance?

Blanche d' Artois is the cousin of the French King Philippe and childhood friend of Ellen de Montfort. She marries Edmund Plantagenet. Blanche's appearance with Edmund is a comfort to Ellen. Ellen's confinement is relatively comfortable and she is allowed to attend parties at Edward's court even as a hostage. Blanche is at these parties and dinners with Edmund and the women are allowed time together. Blanche does all she can to ease Ellen's suffering, and even suggests that Ellen flirt with Edward so he will not be so harsh with her.