I ended up making her two dresses. The client had only requested one but seriously, whoever heard of a Barbie doll with only ONE dress.
The first dress was based on a 'Review' brand dress I was altering for another client. It was a lovely shape that just suited Barbie. When this client came to pick up her altered dress, I told her I had copied her dress and she was quite happy about that. Then I showed her what I had done and she was enchanted, she thought it was so cute.
Just before I sent the doll off, I added a headband made from the fabric scraps. (Sorry, no pictures of that.)
For the second dress, I used the pink satin that the client had sent me and, just as Night Owl suggested, made a princess dress. This one is all lined and has a tulle underskirt. I would have liked to have added another layer or two of net underneath to make the skirt even fuller but I also didn't want to make the skirt too big so I left it at one layer.
I also made a rose and put it on a hair clip to hold back some of her hair.
I'm not sure what her original hairstyle was like but now you can see her pretty face properly.