I just finished reading In Code by Sarah Flannery. Sarah's book is about her love of mathematics and a project that won her great acclaim in building a new public key cryptography algorithm. The book is light on math, enough to get you interested and is approachable to a variety of skill levels. Sarah was a mere high school student when doing all of this and challenging the famed RSA algorithm. Ultimately her CP algorithm is found to be vulnerable to an attack lessening it's usefulness but not her story.
The book is an interesting read about a brief moment in this brilliant woman's life. I think this would be a great read for girls that are interested in math but are far too often discouraged from embarking on it due to societal concerns.