Wings (Laurel Book 1) by Aprilynne Pike

What's on the back of the book:
Laurel has always lived as an ordinary girl - but now something is happening to her.
Something magical.

In this enchanting tale of magic, romance and danger, everything you thought you knew about faeries will be changed forever.

A piece from the book:
Saturday morning dawned cool, with only a light mist that the sun would probably burn off by noon. Laurel predicted a hundred per cent chance of everyone at the bonfire diving or being pushed into the chilly Pacific water, and was doubly grateful she had bowed out. She lay in bed for several minutes watching the sunrise with its blended hues of pink, orange and a soft, hazy blue. Most people enjoyed the beauty of a sunset on a regular basis but, to Laurel, it was sunrise that was truly breathtaking. She stretched and sat up, still facing the window. She thought of the percentage of people in her small town who were sleeping through this incredible sight. Her father, for one. He was an infamous sleeper and rarely rose before noon on Saturday - or Sleepday, as he called it.
She smiled at that thought, but reality trickled in all too soon. Her fingers walked over her shoulder and her eyes flew open wide. She bit off a shriek as her other hand joined the first, trying to confirm what she was feeling.
The bump was gone.
But something else had replaced it. Something long and cool.
And much bigger than the bump had been.
Cursing herself for not being one of those girls with a mirror in her room, Laurel craned her neck, trying to see over her shoulder, but she could only see rounded edges of something white. She threw back the thin bedsheet and ran to her door. The knob turned silently and Laurel opened the door a tiny crack. She could hear her father snoring, but sometimes her mother got up early and she was very quiet. Laurel let her door swing open - consciously grateful, for the first time in her life, for well-oiled hinges - and slid down the hall towards the bathroom with her back to the wall. As if that was going to help.
Her hands were unsteady as she pushed the bathroom door closed and fumbled with the lock. Only when she heard the bolt click into place did she let herself breathe again. She leaned her head against the rough, unfinished wood and forced her breathing to slow. Her fingers found the light switch and she flipped it on. Taking a deep breath, she blinked away the dark spots and stepped towards the mirror.
She didn't even have to turn to see the new development. Long, bluish-white forms rose over both shoulders. For a moment Laurel was mesmerised, staring at the pale things with wide eyes. They were terrifyingly beautiful - almost too beautiful for words.