In the book and screenplay/movie, Wuthering Heights, Nelly is the character of a house servant in the home of the Earnshaws. She excessively pries her nose into other people's business, putting her word in, and working mischief. In the book, she does not seem to really care about anyone much except when she is causing conflicts. However, in the screenplay, she seems more caring and attentive to problems regarding the family.
In the 1847 book Wuthering Heights, by Emily Brontë, Nelly questions Catherine's love for Edgar, knowing that Heathcliff is in the other room listening in. While Edgar and Catherine are married, Catherine stays in her room for days sick, not eating, losing sleep, and looking pathetic because of an earlier dispute between them. All the while, Nelly never mentions any of this to Edgar, making him miserable. When Catherine asks what Edgar is up to and why he never comes to see her in her dying state, Nelly implies that he is in the library reading, when she says Edgar is among his books. In reality, he had been trying to read, but he has been disturbed by Cathy's absence and unwillingness to see him. Both of them are miserable because there has been a lack of communication on Nelly's behalf.
Nelly never really tries to help Cathy deal with her problems maturely either. Cathy is a stubborn girl, although Nelly is a wiser peer and could have helped to lead Cathy in a better direction regarding her choice of actions. Nelly just stands by and lets chaos take its course, and she allows lives to go to ruin in the bittersweet conception of distrust and lies.
However, in the 1939 movie, directed by William Wyler, Nelly (Flora Robson) is more concerned for the well-being of Catherine (Merle Oberon). When Catherine runs out in the rain after Heathcliff (Laurence Olivier), Nelly is very concerned and sends for help. She cares about Cathy and know she is making a mistake by marrying Mr. Edgar Linton (David Niven). She tries to be helpful when asking Cathy about her love for Linton. She appeals to Heathcliff and gives him hints about where Cathy is, and she does the same for Cathy regarding Heathcliff. She willingly sneaks him in while Edgar is gone, so that they may continue their love in her sickness. She does not seem to pry into other's business as much in the movie either. She keeps to herself and hopes for the best in situations of concern.
Nelly is a completely different person in the opposing stories of novel and screenplay/movie. She acts a little jealous and insensitive in the book, causing problems where she can, and making mischief that causes heartache and drama; whereas, in the screenplay/movie, she is there to listen and be a helpful guide to Cathy, giving her the advice she
knows, and watching over her during many arising conflicts.