I received the jumper for the Birthday outfit when I bought the doll version. It was a girl's "Large". I wear a size 6 usually- and the dress fits me for the most part.
I did have to make some adjustments. I had to move some buttons to fit my chest, as well as added ribbons to cinch the waist. I am 5'5", and the dress reaches the middle of my calves. Which still works fine for me- but the doll version is proportionately longer.
The fabric is very durable, although it wrinkles easily. The purple color is lovely. The fruit print may not be for everyone- I did stand out as being dressed out of current style, almost costumey, when I went to the North Point mall wearing it. It would probably seem less out of place on a tween or teen than on an adult.
I have no clue if they sold a shirt with it- but I wore a regular white t-shirt from Mossimo/Target and it worked quite well.
Overall an A for the dress per se. I would give it an A+ if it would fit my measurements- but I am all grown up. I am positive that when I was 12, my figure would be closer to what the dress is.