Queens of Spells & Stone (Vessels of the Gods #1) by Katerina Stevens:
 
On the magic imbued continent of Irridessen, there can only be one Queen on High.

Two Princesses must forego their delicate sensibilities to reveal the bloodthirsty beasts roiling under their perfect skin if they want a chance at securing the coveted title

…When a rare flicker of power flares within the confines of the magic-barren Slate Kingdom, two disgraced King’s Guards hunt for the source – hoping to uncover the truth behind the vicious murders of their Late King and Queen and bring a killer to justice…

…Lenna struggles to accept her role as the quiet, subservient wife to a powerful Lord in the Slate Kingdom. At fifty-one years old, she reminisces on the freedoms she had during her youth, while slipping further into the doldrums of life. Migraines morph Lenna’s dreams into nightmares of leathery wings and giant stone monsters, revealing a deadly truth that she quickly learns could be a blessing – or a curse.

Will she break free from the chains of her stagnant life? Or will Lenna be devoured by the same monsters that haunt her?