You know, before I saw the series, I actually thought the Magical Girl to Witch transition actually like this.
What witch? I see a ballerina.
I believe she is reffering to witches from Madoka Magica. Witches are creatures born from greif, created when magical girls die. Witches are really creepy...and often reflect on their personality. If someone wanted to be a princess, and died trying, they're witch might look like a queen/princess.
It really does look great, I'm glad I got this from you because it suits the style well! ;w;