The princess who flew with dragons
(Book)

Princess Sofia of Drachenburg is sick of being used for her older sister's political gains. At twelve years old, she's already been a hostage to invading dragons and promised to marry a wicked fairy. Now she's being sent to far-off Villene to play the part of a charming, diplomatic princess. Her only comfort lies in writing letters to her pen pal and best friend--Jasper, a young dragon she's never even met. But when an accident leads to her exile from Villene, Sofia is free to wander as she pleases for the first time in her life. And when Jasper's magical sister Aventurine turns him into a human boy, Sofia thinks life can't get any better. Until . . . the legendary ice giants of the north attack, trying to reclaim the territory that was theirs centuries ago. With the dragons and royals frozen in ice, can Sofia and Jasper save their families and kingdom? -- from Amazon.