Amaranthine by Brenda Robertson

Set in 1885 London, and the forests of Denmark, Amaranthine is a Gothic love story. Astral has lived in near seclusion with Davn for six years: ever since he found her lying half dead on the road. She is happy, and safe, and she's nearly forgotten the horrible things she did that last night in her father's house. But now Davn is sending her away, to London, to live with strangers. And the questions will begin. Caught between protecting her secret past and living her new life in the opulent city, it's her memories of Davn that keep her awake at night. But Davn has his own demons; and now they're coming for her. In the end, it won't be the horrible things she did, that will threaten her life.