Anastasia

Anastasia is an antagonist that appears in Castle of Dreams in Kingdom Hearts Birth by Sleep. One of Cinderella's wicked stepsisters, she is loyal to Lady Tremaine, her mother, and will do all in her power to get in cohorts with the handsome Prince Charming by making Cinderella's life miserable.

Kingdom Hearts Birth by Sleep
When a ball is held at the Castle of Dreams, all unmarried women are invited for the prince to find a bride. Anastasia, along with Drizella and Lady Tremaine, attempted to keep Cinderella from going along by giving her endless chores to finish and preventing her from finding a suitable dress.

When Ven and Jaq make it for her, she and Drizella tear it apart saying she had stolen their materials. But their plot failed when the Fairy Godmother makes a new dress for her and a pumpkin carriage to transport her to the ball. She is unable to identify Cinderella during the party as she is too far away from Anastasia to be recognized.

After the ball, Prince Charming asks the Grand Duke to search for Cinderella with the glass slipper. When he finally reaches their house, Anastasia attempts to make the shoe fit her oversized foot, but Cinderella proves to be the true owner of the slipper. The Duke takes Cinderella with him back to the Castle, only to be confronted by Lady Tremaine and a powerful Cursed Carriage who intend to dispose of Cinderella. This act, however, causes the three women to be hit by one of the Unversed's attacks. Aqua then states that they were crushed by the darkness in their hearts.

Origin
Anastasia first appeared in the 1950 Disney film, Cinderella. She was cruel and unkind to Cinderella, and does not want her to go to the ball. When the footman tries to fit the glass slipper on Anastasia's foot, she at first thinks her foot fits, but it does not. Anastasia later appears in the film's sequels, Cinderella II: Dreams Come True and Cinderella III: A Twist in Time, as well as the TV series, Disney's House of Mouse.

Trivia

 * Anastasia is one of the few film antagonists featured in the Kingdom Hearts series who is not a boss.
 * Anastasia was only an antagonist in the first film and the Kingdom Hearts series. Over the course of the films, Anastasia gradually changes her ways and becomes an ally to Cinderella after Cinderella helps her find her true love.