Being the princesses their dresses are resemblant to Elissa, the queen, but slightly simplified. They too have the apron and the backdrapes, but a narrower skirt and only one hanging spear/tab in front. They also have a different bodice, with a sort of green "bra" crowning a corseted waist (some have all red corsets, some echoes the stripes of costumes used by Carlotta and Christine). There are various trims and decorations on the bodice as well.

As we're supposed to be introduced to the opera house in the middle of a dress rehearsal, several on stage are wearing their "personal" clothes or items. For these ladies, two of them are wearing the princess costume, while the third one is still in her everyday dress (to the right). One of the others are also wearing a cape, probably to protect throat and shoulders from the cold. Both of these personal items are based on outfits from the Victorian fashion magazine "Harper's Bazaar". There's also an uncanny likeness between the costume sketch and the picture of Mata Hari - I would be surprised if this similarity is accidental.

As revealed in the costume sketch, one of the persons playing the princess is the same playing the mirror bride in MOTN: "next appearance Kristin double w/wedding dress" - basically, the Christine understudy.