The Sorcerer's Daughter - Five Towers Duology, #1

A sorceress with no magic. A stolen crystal that holds the key to her future. And in a court of royals.a treacherous fate she can't escape. Seventeen-year-old Violet Winthrope is destined to marry a nobleman, if her father has anything to say about it, and he usually does. But Violet yearns for more out of life than being a wife and mother. She dreams of being a powerful sorceress. The problem is she has no magic. Until the day she stumbles upon a fragment of a crystal that appears to have stars inside.
Enthralled, Violet is compelled to steal it from her father's study and keeps it hidden on her person. When her father is suddenly called to court as the king's royal sorcerer, he packs her up and heads to the castle. Nothing has prepared her for the treachery, machinations, and deceptions thrown at her in the royal court. When the crystal she's been hiding suddenly springs to life, responding to her every whim, Violet's dreams of becoming a powerful sorceress seem to be within her grasp.
Or will her ultimate power prove to be her ultimate destruction?