Anonymous wrote:What does the 6 year old WANT???
Let her pick her own costume, don’t make her do your matchy costume. Let her decide.
This - although my older-DD and younger-DS kids have enjoyed matching in the past, sometimes extended to include others in the neighborhood.
Harry Potter, Star Wars, and Marvel give you lots of options. I know from experience

harry potter costumes can be really easy, comfy, and not too skimpy which is nice bc who wants to wear their winter coat OVER their costume lol!