There is a great book series by American Girl and I highly recommend all their books. There is one titled A Smart Girls Guide to Middle School. Consider also getting her the ones A Guide to Friendship Problems, The Care & Keeping of You, The Feelings Book, and Stand Up for Yourself & Your Friends about bullying.
My 8th grade daughter still pulls them out and re-reads them occasionally and now she's sharing them with her 10 year old sister. They are beautifully written and incredibly informative in an age appropriate way.
I think the jewelery is a great idea too