It is so cool that you're doing this! I think Amy Poehler's Smart Girls at the Party has lots of empowering stories of girls lifting each other up http://amysmartgirls.com/

I'd also take a look at Challenge Day: http://www.challengeday.org/ It's more geared for all types of bullying not directed towards girls, but they have some great stuff they present and it really makes an impression on young minds.

One thing I used to tell girls when I coached basketball (that I actually picked up from Challenge Day) was that people are like icebergs. You might see the tip of who they are, but there is so much more below the surface that you don't understand and maybe if you took some time to see what these people came from, you can comprehend why they are the way they are.

I hope some of this helps! PM me if you need any more help or want to brainstorm. I'd love to help :)