Some characters might become more open - minded. If they are used to the traditional Cinderella story, seeing the different interpretations in the fanfiction could make them realize that there are many ways to tell a story. For instance, a character who always thought Cinderella was just a damsel in distress might see her as a strong, independent figure in the fanfiction.
Their views would likely vary. Characters who are more conservative might reject the changes in the fanfiction at first. But as they think more about it, they could come to appreciate the creativity. For example, if the fanfiction changes the setting of the Cinderella story from a medieval - like kingdom to a modern city, the characters might initially be shocked. However, upon further reflection, they might see how the modern setting allows for different types of challenges and character development for Cinderella. This could make them more accepting of new interpretations of stories in general.