The Listeners, by Maggie Stiefvater

The Avallon Hotel in the mountains of Virginia is a luxury spa resort that caters to every whim of the rich and infamous. Protégé of its owners, the Guilfoyle family, June Hudson has been the General Manager for 10 years, devoting her entire life to keeping the magical waters sweet and the hotel in balance. When the attack on Pearl Harbor draws the US into the war, the Avallon is commandeered to house enemy diplomats prior to their deportation. June is stretched to her limit, dealing with the FBI, the Feds, her unwelcome guests and the staff, many of whom she is losing to the draft. Can she keep it all together until the hotel is rid of its enemy aliens and will life ever return to what passes as normal at the Avallon? War changes everything, including June, and she finds herself questioning her priorities and her future. This is a strange tale, based on true events but with a magical twist and a very engaging heroine.