Girls are more often than not mean at that age. It’s a sad reality. And it’s a tough age, on top of that.
What you have describe signals to me that she’s in the wrong friend group. She needs to find her tribe — girls that accept her for who she is and want to spend time with her. Try a different Girl Scout group until you find one that works better for her. Get her involved in other activities where she can meet kids who have similar interests/passions, which often softens the barrier of differences.
Keep reminding her that people who don’t treat her well are not good friends (their own flaws/weaknesses), and that is not a reflection on her, but of who they are. Remind her that she wants to be with people who treat each other with kindness and respect, like she treats her friends.
And it’s ok for her to make friends who are a little younger. They will be more aligned in maturity and social skills.
Here are some more insights:
ADDitude Community Moderator, Author & Trainer on Parenting ADHD, Mom to teen w/ ADHD, LDs, and autism