It's Ingenue's "Christmas Girl". I am looking around at Ingenue as I type, and while I don't see it, the "Tracy" outfit and "Birthday Girl" have skirts of similar design. They look wonderful, and I feel wonderful when I wear it--especially with shadows enabled.
Even if you're not as taken with this particular skirt as I am, Ingenue has lovely vintage fashions, and is well worth exploring. (Now to find some hairdos of that time...)