Nelly Dean was an inaccurate narrator even though she witnessed most of the main novel events. Her views of the story were biased. She underlined her disapproval of Catherine Earnshaw and favored Hareton.
Ellen “Nelly” Dean is one of the central characters in the novel. The female narrator of the book tells Mr. Lockwood the first-hand story about Catherine.
Nelly works as a maid in Wuthering Heights. She is loyal to the owners (the Grange and some part of the Earnshaw families). But her biased perception influenced the narrative. Bronte uses the character not to cast moral judgments of the families but to dramatize and drive the plot.
For many reasons, Nelly Dean can be considered a very untrustworthy source. First of all, she is explicit about her dislike of Catherine Earnshaw. When the events deserve to give Catherine some sympathy, she hardly expresses any of it. On the other hand, Nelly favors Hareton, Cathy’s brother. The biased approach to Cathy is the first evidence of Nelly’s being an unreliable storyteller.
Another argument is the inconsistent timeline of her story. She mixes up what she witnessed and what someone else told her. She saw most of the events in Wuthering Heights, but there were some that she missed. She filled in the gaps with gossips. Meanwhile, Mr. Lockwood does not have any other source of information. Her point of view affects Lockwood’s perception of the events, and the readers are affected, too. Nelly’s habit of making some characters seem better or worse compared to what they are make them more dramatic.
In addition, Nelly Dean was ousted from the mansion at least two times. The reason could be her bad attitude towards some of the residents. It happened when she left Heathcliff on the landing of the stairs upon his arrival in the mansion. Even though the maid was present while Heathcliff grew up, he never earned her affection. And she was certainly there and remained idle while the boy was humiliated.
Nelly is a villain who caused many conflicts. Mr. Lockwood cannot ask anyone else about the truthfulness of the events. His journal is a symbiosis of Nelly’s version filtered through his perception, unreliable but dramatic.