The city on the other side

Quiet, high-society sheltered girl Isabel lives in San Francisco, where she keeps her dresses spotlessly clean, is impeccably behaved, and certainly never has adventures. However, the Great Quake of 1906 has changed things--one day, Isabel finds herself crossing a barrier into another world, where the fairies of the Seelie and Unseelie Courts are at war. Only Isabel, with a magic necklace and a few new friends, can end the war before it destroys both worlds.