It all depends on Tennessee law. Does it provide for ‘certification as an adult’ for 12-year-olds? I think most states do not. Adult or juvenile she’ll likely be free before too long and her cousin will still be dead.
This also begs the question as to why two sub teens would even have access to a smart phone to argue over in the first place. Dumb phones do everything that kids that age need to do: call home.
I have seen evidence of 7 y/o kids with cell phones.
BEYOND STUPID-———
Your expenses are too high?
Start with your cell phones, people.
Dumb phones don’t get stolen and thus available to kids