October Daye - Series by Seanan McGuire
October "Toby" Day is a former street kid and half-breed Daoine Sidhe who's practically made a career out of running away from things. She was raised in the Summerlands, last of the true fae realms, only to flee to the mortal world when she was a teenager, looking for a life she could call her own. For a while, it looked like she might even succeed. She found a place in the service of a local Duke, earned her position as a knight errant, fell in love, and thought the running was over.
She was wrong.
All too soon, all she wanted was the opportunity to run away from everything and fade into obscurity. Unfortunately for Toby, life is rarely simple for changelings, and her own talent for complicating things makes it impossible for her to disappear into the shadows. It probably doesn't help that she attracts trouble the way that candles attract moths, or that she's somehow managed to catch the eye of some of the most powerful people in the Kingdom of the Mists...