Both of these Bibles start each book with an easy to understand introduction that tells a little about the book and when and where it was written. They also include some of the main players. They also both have devotions throughout.
"NIV Bible for Teen Girls" also includes a concordance and character profiles of women in the Bible. I like the way it has highlighted the promises of God. I see this Bible for more of an older teen.
The "Faithgirlz Bible" is also NIV. It seems to be written and put together for a younger teen, as well as an older teen. Honestly, I would even use it as a personal study Bible. I love the way it includes recaps about half way through each book, and then asks the reader to finish the book and write a recap of their own. It also includes little quizzes about yourself throughout, and then shows where to go to learn more. It answers questions that many people have, such as how people can be so old in biblical times. It has life applications. And, I love the way it pulls certain verses out and puts them in a cloud, called TREASURE THIS!! In the back it shows HOW TO BEGIN A RELATIONSHIP WITH JESUS and provides a space to record when you began that relationship. It includes PROMISES (what to do when...) & PERSPECTIVES (what the Bible says about...). Of course, it includes a READ THROUGH THE BIBLE IN A YEAR schedule. And, there's even a few pages for notes.
Both of these Bibles are hardback, so they are more durable, and pretty, so a young girl would like to carry them around.
I like both of these Bibles and would recommend them for your teen girl.