Diagnosis?

I have twin 8 year old daughter'. They are doing well but I feel one of them has autistic tendencies. They don' appear to be affecting her at school too much. But they can sometimes be an issue at home. 

I don't want to get her diagnosed because I feel being labelled especially at school puts you at a disadvantage and you are treated differently but I would really like some tips and techniques to help her cope with life and her struggles.

I' pretty sure it would high functioning anyway as she is very clever and doesnt have any speech problems. I think dancing has very much helped her to control and improve her physical difficulties and I would really like to help her other issues, like meltdowns and coping when things go wrong or when she is over stimulated. She has taken to hitting herself in the head and calling herself stupid lately and I don' want this to continue.

Any help and advice would be appreciated

Amy