Who is Ellen de Montfort from The Reckoning and what is their importance?

Ellen de Montfort is the daughter of Simon and Nell de Montfort. She is a rare beauty who follows her mother into exile in France after the death of her father. She is twelve years old and engaged to the Prince of Wales, Llewelyn ap Gruffydd. After the death of Simon, the de Montforts lose their lands, their money, and their titles. As expected, Llewelyn breaks the engagement, but Ellen has romantic dreams that he will one day come for her. As the years pass, she accepts that he will not come. Her prospects for marriage are slim because her family no longer has a dowry of lands and income to offer prospective husbands.