Lady Reaper by Christina Bauer
Lady Reaper is a novella set before the first Angelbound book. Myla is a 16-year-old girl who fights demons to the death in the arena. She is always in the mood for a fight. When Myla discovers that the famous ghoul Lady Reaper will be in the Demon Woods on the annual festival and she is excited to look for her. But Lady Reaper has plans for her and Cissy too.
Myla is one of my favourite characters and I loved reading about her before she was scala when she was just a kick-ass arena fighter. And that ending... OMG, I can't wait for the next book! :)