The Spellsong War

Anna Marshall wished she could be anywhere but Ames, Iowa, and anything but a singer and music instructor at Iowa State University. She made her wish at exactly the wrong time and found herself pulled from Iowa to the very different world of Erde. On Erde, song is magic, and Anna's musical ability makes her an enormously powerful sorceress - potentially. Life on Erde is harsh compared to Ames, but at least it's not boring. On Erde, Anna is in charge of her life for the first time - and she's making the most of it. With her unique power, her common sense, and her Integrity, Anna saved the kingdom of Defalk from invasion and in six months became its regent.
After years of war and drought Defalk is hardly able to defend itself, and Anna must turn her efforts to rebuilding the kingdom before another neighbor tries to conquer it. But she may have no time: Defalk's southern neighbor is already encroaching on the border. In the realpolitik atmosphere of Erde, Anna will have to teach a harsh lesson to demonstrate that she will not allow Defalk's greedy neighbors to nibble her country to death. And since the sexist rulers of most of the neighboring kingdoms are still convinced that women are weak, Anna may have to make the lesson she teaches doubly harsh.
Rising to power in Defalk may have been the easy part; now Anna will need all her skill and intelligence merely to hold on to what she's managed to accomplish so far.