One of my neighbors has a 7 year old who made up her own costume for Halloween. She was "the girl in black." I ended up seeing these books called The Princess in Black on Amazon. I bought one for her on a whim and it turns out, she had already read the first one and she was totally excited for the one we got her - the next in the series.

They're a perfect book for 7/8 year olds if you're looking for something like that. http://www.amazon.com/Princess-Black-Shannon-Hale/dp/076366510X/ref=tmm_hrd_swatch_0?_encoding=UTF8&qid=1447429112&sr=1-1