Her Personality:

Violet Beauregarde has been described in the novel as a "beastly girl." She has a tendency to disrespect her parents, occasionally snapping at them with phrases like, "Alright, Mother! Keep your hair on!". Her disrespect of authority leads her to flat-out ignore Mr. Wonka's warnings about the Magic Chewing Gum, which led to her being taken to the Juicing Room and exiting the factory shortly after. It is unknown if this incident leads to her learning anything afterward.

The most notable aspect of her personality is her tendency to chew gum with her mouth open, constantly. She takes great pride in her record-winning gum, which she had chewed on for months. She only takes it out when eating meals, sleeping, or possibly swimming. Like some kids, she is rotten.

Ref: https://www.youtube.com/watch?v=8Yqw_f26SvM&t=31s