I made her what she wanted, and in the end I was glad because she was the cutest damn witch I'd ever seen.
Fast forward to now and my 4 year old son wanted to be a witch for Halloween. I asked him what a witch wears and he said a dress, so we headed to the Pinterest search again and he loved the fluffy tulle numbers. He wanted to be a "rainbow witch". All my dreams from five years ago had come true!!
My daughter's dress was made using Butterick 4319, with the hat coming from Simplicity 3680 I believe. All made out of black poplin from memory.
For my son's dress I wanted to use knit as I had a roll of black jersey, and wanted to use a pattern I already had. I went to the Stitch Upon a Time Girls Shirtzie pattern. Advice from their Facebook group was to size up because it's a snug fit and boys aren't usually used to that in clothes. He measured between a size 4 and 6 around with a 4 in height. But when I compared the finished measurements to one of his (smaller) t-shirts, it was more like a size 10. In the end I decided to cut a size 4 bodice with a "full bust adjustment", pivot method, to take it out to the size 10 line on both front and back. I do FBAs for myself all the time, so this seemed like an easy solution. It kept the smaller shoulders but added girth to cover his round middle. I then cut the skirt size 10 at the waist, but a 4 length. It turned out the perfect size, easy to get on and off, but not so loose that it lost it's shape.
For the bodice, I sectioned off the front and redrew the neckline to get the front panel, and then attached rainbow ribbon.
For the skirt, I was using 6" wide tulle off a roll. I decided that 6" scrunched pretty nicely into about 1" so I did some maths and cut 9 strips of each colour, which I then divided into 3 rainbows around the skirt. I just bunched up the tulle and pinned it in place all the way around then sewed it down before gathering the skirt into the waistband.
And that's how I made my rainbow witch, using the hat from 5 years ago with tulle added, and a pair of his sister's slightly too small rainbow leggings. I loved it, and he loved it which is the most important part.