'The Uninvited' is a remake of a 2003 Korean Horror film Janghwa, Hongryeon (2003) (literally "Rose Flower, Red Lotus") or "A Tale of Two Sisters," starring Su-jeong Lim and Geun-Young Moon. It was directed by Ji-woon Kim and is the highest grossing Korean horror film to date.
In the movie, Anna is meant to be fourteen/fifteen years old - in reality, Emily Browning was twenty years old at the time of filming.
Emily Browning originally auditioned for the role of Alex.
The book Anna's father gives her in the car is titled The Repose of Sand. It's also the book she's seen reading later, in bed.
A variation of clever camera angles and forced perspective helped maintain the illusion Elizabeth Banks was several inches taller than Emily Browning who in reality is only two inches shorter.