Based on this reference by DA user RazorBladetheUnicron and using this Twilight by DA user StellarDusk as the base, as requested by 3D4D.
As you can see, I decided on some sort of mix between the AU Twilight’s cape and the one cannon Trixie wears.
The star you can partly make out behind her head is supposed to be part of a barrette.
Also, I learned the word “barrette” today, what a productive day.
Like if ‘Miss Lulamoon’ wrote a wildly popular series of books about a young unicorn named Trixie and her adventures, but everything in them actually happened.