Prion Universe - the Matriarch (Isles of Cressida)

The Isles of Cressida are formally ruled by Lady Cressida, a woman in her 20's who came into power after her parents died when she was a teen. She's still learning how to assert herself in a position of authority and navigate the politics of the faction.
Lady Cressida is allowed to defer most of her power and decision making to her grandmother, known in the faction as Gunxian Mother. Gunxian Mother is respected by the people as the true unofficial ruler of the Isles.