The magical Prism Salt!
I tried to cherrypick the training set (glad we had a lot more high quality illustrations than festival for some reason) and the outcome is pretty good as I can see.
Also, following @Tyuikl32 's suggestion I tried training with Illustrious-XL and generated with NoobAI, instead of Pony. Might as well train a pony one later if I have the motivation.
Use these words to trigger:
salt\(maimai\), thick eyebrows, ahoge, hair between eyes, cat ears, cat tail, animal ear fluff, green eyes, (grey purple hair:1.1), hair ornament, small breasts, star ribbon,star \(symbol\), star decorations, crescent hair ornament, blue elbow gloves, frills,
You can also use prompts to have open/closed/no umbrella as from maimai.
Quite often the star on her waist bow will be drawn as crescent, but should be good with more attempts.
All maimai and maimai DX related materials are Property Of SEGA