To be totally honest I do not know, it was my niece's and she is a B cup so it would be hard to say, but if you can wear an average small then I don't see why not.
It is a small, it was my niece's for homecoming last year and she is a size 0-1 and it fit her good and maybe a little, very little more room. I would say size 0-3.
I hope so too. How old is your little girl and did you see the new picture of my niece in the dress? It gives you a better idea of what it looks like on.