The Book of Stone (2009)

Remake of Carlos Enrique Taboada's classic film from 1969, IMDB says: "Julieta is a young child psychologist hired by millionaire Eugenio Ruvalcaba, to work with his only daughter, Sylvia, who has severe emotional problems, while staying in their isolated island mansion. Once there, she finds out there's much more to Sylvia's imaginary friend than what everybody knows... and the results can be horrifying..."