Who is Millicent from The Lion's Lady and what is their importance?

Millicent is Lyon's mother. She is, according to Lyon, "a professional mourner", who has spent three years in bed, grieving over the death of her son. Christina cannot abide that Lyon allows his mother to wallow in self-pity, and she forcefully encourages her to begin rejoining the family. Millicent is reluctant, but she slowly makes steps in that direction under Christina's insistent influence.