There are a lot of books written about WWII, but not that many for young adults, especially not with girls as the protagonists. Elizabeth Wein, however, has written an excellent book called Code Name Verity. The story is mainly about two girls who become friends and help out in the war effort, in different ways. They have different backgrounds and personalities, but they work together and form a lasting friendship.
Code Name Verity is written most in journal-type form, but done well so the story moves along and holds the reader’s interest. It is well-written and definitely worth checking out.