Hi there I can talk with you. Your question posted quite a few hours ago and I am not sure if you are still available to chat.
Please repond if you are interested when you get notice of my reply and we can talk back and forth which may be more helpful to you....but I would leave you with some thoughts to ponder first.
Where is she in terms of puberty physical staging? Has she started to develop any breast tissue/pubic hair/growth spurts?
What is her life at school and outside of school like, any new tensions, does she have any extracurricular activities to help her keep busy and exercise? Is she in fact overweight? Any mental health illness in the family? What sort of coping help have you tried already (counseling?)
What grade is she in, does she like school?
Around this age group girls and boys when they start having more hormonal influence (bodies changing puberty etc...), can have a really tough time emotionally even if she has barely started showing physical signs the behavioral changes can start before the physical ones. I can definitely give you some suggestions on how to best help her but I don't want to lay out things you have already tried so when you get word and if you are interested in chatting let me know thanks!!