Hi S.,
The benefit of the diagnostic label is that she would become eligable for more services, and you would have professionals aware of her needs. They would be able to adapt situations and offer additional support. You will also be informed of a wealth of services and programs.
I am a speech-language pathologist, who worked in the public schools for seven years, before starting my own private practice nine years ago. I had worked with many children that fit your child's description. The parents were so much better informed, because the school staff knew the child's needs, and could inform the parents about new social programs, groups, clubs, etc.
This is an important time to seek services in that area. You daughter is fortunate that you are concerned, and willing to explore a variety of avenues to help her develop to her full potential.
Good Luck!
S.