"Agatha [...] invented a character, Ariadne Oliver, who is a fictional take on 'Agatha Christie'. Mrs. Oliver, who first appeared in Parker Pyne Investigates, is a large grey-haired woman who writes murder mysteries, eats apples and is saddled with an imaginary detective - the Finn, Sven Hjerson - whom she cannot bear ('Of course he's idiotic, but people like him'). It is a wonderful joke, and Mrs. Oliver is a wonderful creation, but she is not Agatha; although occasionally she does speak in her authentic voice:
A deal table, her typewriter, black coffee, apples everywhere ... What bliss, what glorious and solitary bliss! What a mistake for an author to emerge from her secret fastness. Authors were shy, unsociable creatures, atoning for their lack of social aptitude by inventing their own companions and conversations.
'...The truth is I'm not very good with people.'
'I adore people, don't you?' said Robin happily.
'No,' said Mrs. Oliver firmly.
'But you must. Look at all the people in your books.'
'That's different ...' "
From Agatha Christie: An English Mystery by Laura Thompson.