My daughter suggested some dress-up clothes for GD for Christmas. I thought it was a great idea as I can make some and transform some old things, and buy a few accessories. I wonder would something like that that suit your GD, kittylester? If she likes writing plays, she may like acting them out too. I used to love dressing up, as did my children and we always had a "dressing up" box.
If she likes Strictly, you might find some suitable dresses in a charity shop - but even your own wardrobe might be a source of some things.