The Shattered Cage - The Dreamwing Trilogy, #3

After leaving her best friend behind in Dreamwing, Randi is losing hope of ever returning there. She's no hero, and everything she does ends in disaster. Trapped on Earth, with Excalibur rusting under her bed, Randi is forced to face the terrible reality of a world where she never truly fit-without magic and, worst of all, without Tessa. Fortunately, not all damsels need to be rescued.