It stands very well on it's own with no context at all. The girl is dressing up. she is looking in a mirror and assessing. Is there a greater message. I think so. Why is she doing this? One might assume she is entering a stage of self conciousness looking to see how she looks in the adult shoes and princess outfit. (I do not have daughters so I will assume it is a princess outfit). I suppose someone could assign a more social/gender role type of interpretation to the image. From an educator stand point one could draw several connections to Piaget and his theory that play is the work of the child.
If you wanted to make the point that a picture needs context to make it work, there were many others in that photo essay that, in no way, could stand on their own without context. But, in the context of the Essay, "Girl Culture", work fantastically.