Showing how Catherine has altered her personality after being forced to live at Wuthering Heights and developing her "new" character helps the reader truly relate to how she must feel imprisoned in the house. Also, more and fore of Hareton's character has come out to help show the harshness of Catherine's. By playing Catherine off of Hareton's ever developing personality, the reader catches a glimpse of Bronte's purpose of creating a believable world.
Also, her writing devices, imagery, repetition, syntax, and diction all help keep the story real. Each device allows the characters and stories surrounding them in a light tainted in reality. Such description and structure create scenes and events that the reader can relate to and actually see themselves transformed into.
Second, the pile of rabbits foreshadows the strange behavior of Mrs. Heathcliff. Later on in the chapter, we find that she deals with the "Black Arts." Perhaps these rabbits have something to do with her witchery. Even though she says they are not hers, they may be a cause of her workings. Still, the rabbits tell a lot of the atmosphere in the house.
The images evoked by Cathy's monologue show how much more she loves Heathcliff. How her "love for Heathcliff resembles eternal rocks beneath: a source of visible delight" and how her "love for Linton is like a foliage in the woods: time will change it" makes the blatant contrast between the two relationships. Bronte's diction in this passage also proves the complexities in each relationship. Cathy knows she will "perish" if Heathcliff leaves, but if all else "perishes" but Heathcliff, she will go on. She claims that "everyone should have an existence...beyond [themselves]. Such diction shows the almost religiousness or spirituality she feels towards Heathcliff. Such a relationship should not be separated, yet Bronte chooses to do just that and has Cathy marry a man she does not feel nearly as strong for.