No Place for Magic (The Tales of the Frog Princess) by E.D. Bakerabc

When Emma and her beloved frog-turned-prince Eadric travel to Upper Montevista to ask for Eadric's parents' blessing on their marriage, they find his homeland in chaos: Eadric's annoying little brother Bradston has been kidnapped by trolls! Worse, his mother won't let Emma use magic, even to rescue Bradston, and Eadric seems suddenly a bit too fond of the girls from his past. But as they travel through unfriendly lands, battle sea-monsters and vampires, and find allies in unlikely places, Emma just might come to see her Eadric for the strong and loyal young man that he is.
With a dose of bravery and a few clever tricks both magic and not, Princess Emma takes center stage again in this utterly charming and surprising addition to E. D. Baker's fantastic Tales of the Frog Princess.