In the novel They do it with Mirrors, Juliet "Jolly" Bellever is Carrie Louise's secretary and companion since Louise's second marriage. She is also the housekeeper at Stonygates, and the one who gives Carrie Louise her medication. She is described as "a gaunt elderly lady", with "an arrogant nose". She has short hair, and wears stout well-cut tweeds. The tip of her nose turns pink when she experiences emotion.
Miss Bellever describes the household at Stonygates as "a crazy household", and laments that one cannot arrange any kind of planned routine. She is very practical and competent.
She later goes to Christian Gulbrandsen's room to see if he wants anything before retiring for the night. She finds him dead from a gunshot to the head, and calls the police.
When the police arrive, she meets them in the Great Hall. She informs Inspector Curry that most of the household are in the library, except for Lewis Serrocold, who remained in Gulbrandsen's room to ensure that nothing was moved.
In Murder with Mirrors (1985), the character is played by Frances de la Tour. In this adaptation, her name is Miss Bellaver. She is rather possessive of Carrie Louise, and refuses to allow Mildred Strete to give Carrie Louise her medications. She says that she does not want anyone interfering. At the end of the movie, Miss Bellaver is fired, as Miss Marple had helped Carrie Louise to understand that Mildred wanted to take care of her.
Juliet Bellever is not featured in the BBC 1991 adaptation of the novel. Carrie Loiuse's daughter Mildred Strete took over the role of attending to her medications. There was also a housekeeper named Mrs Rodgers.
In the ITV 2009 adaptation of the novel as part of their Agatha Christie's Marple series, Juliet Bellever is played by Maxine Peake. Her role is smaller than in the original novel. There is no tension between her and Mildred. However, Johnnie Restarick chats him up and persuades her to leave the lodge gate open for him so that he could get into Stonygates and see Carrie Louise.