This film is one of four versions featuring Lucy Punch as Cinderella's evil stepsister; the other three versions are Ella Enchanted (2004), Cinderella (2008), and Into the Woods (2014).
At one point Claudette attempts to cut off the toes of Goneril and Regan so that the slipper fits. In Grimm's version of the story, the stepmother forces each stepsister to cut off part of their foot (one a toe, the other a heel) to make the slipper fit.
Cinderella's (Marcella Plunkett) real name in the film is Zezolla, after the princess in the Italian Cinderella story, "La Gatta Cenerentola" (or "The Cat Cinderella") by Giambattista Basile, which was published in 1634.
The godmother as a mermaid is a reference to the ancient Chinese Cinderella story "Ye Xian" (a.k.a. "Yeh-Shen" or "Yeh Hsien"), in which Cinderella's godmother is a magic fish. In "Ye Xian", Cinderella also wears a blue gown.
Zezolla plants a rosebush on her mother's grave, and at key moments is guided by a bird that helps her on her quest to get to the ball. This is an allusion to the Grimm version of the story, where Cinderella did not have a fairy godmother, but rather a tree that contained magic birds.