I find it so compelling as it makes me realize that we are who we are from the very beginning. Here we have the three girls. Two are playing, one barefoot, the other watching on in wonder, while the third girl sits a bit behind. Her look says it all .... I really don't belong here (with them).
From the size and the coloring of the original picture, I'd say it was taken in the late 80s. So, these girls should be in their 30s now. I would be my projection that the two girls playing may be hands-on people, ready to experiment and take on the world. Whereas, the 3rd girl, may have grown to become high maintenance and waiting for someone to rescue her.
I love finding things in these envelope !