No, Esme Squalor from the series "A Series of Unfortunate Events" by Lemony Snicket (Daniel Handler) is not a real person. She is a fictional character created by the author.
While the series has many elements that feel real, like the characters' hardships and the dark situations they face, it's a work of fiction, and Esme is one of the many characters that exist solely within the pages of the books.