Spellbinder by Ghillian Potts
Brook, now called Spellbinder, is working as Remembrancer to her friend Graycat, now known as Young Overlord Lady Quicksilver, when Storytellers start disappearing. Spellbinder is captured and forced to summon the Elder Dragons, but when she cannot control them, she must break her Storyteller vow and forfeit her most precious possession her name.