How to help my daughter.

I’ve been working though SCS for myself for the last several months, and I have learned so much! Thank you for bringing this into my life. I’m also down 25 lb (boo-yah!).
My question is about using this material to help my daughter navigate MIDDLE SCHOOL. Dreaded. Ugh. Specifically, navigating friendships amid the swirl of pre-teen drama and puberty hormones. How do you help a kid reach emotional maturity, when their brain isn’t actually mature?
My daughter is 12 and in 7th grade. She’s a smart, kind, funny kiddo. One of my dearest friends also has a 12-year-old smart, kind, funny kid. These two girls have grown up as “BFF’s” through about 5th grade, when they started to make new friendships and spread out into different friend circles. For the past 2 years, we have had rivers of tears and many unkind words from them both as they have grown apart. Junior-high rumor mills, text wars…. you get the idea. I have spend much time with my daughter trying to get her to understand that she cannot control what another person does or says… but she can control how she interprets things and what she does in return. But, it doesn’t seem to be working. At this point, these two former BFF’s can’t even be kind to one another, and anytime they’re together, tears are involved.
The other girl’s mom and I are struggling to help them through it. Our families are intertwined, so simply ending the friendship is not an option. They still have to be around each other on occasion.
Do you have any specific recommendations for helping them understand this? Any resources you might point me to?

Thanks so much for your time, and keep up the amazing work!