From the diary-like entries in Chapter 3 of Wuthering Heights that give the reader a direct insight into Catherine's character, what generalizations can be drawn about her?
Having settled himself in the "clothespress," Lockwood discovers the diaries of Catherine Earnshaw and is amused by her caricature of Joseph, crudely drawn, but accurate in its depiction of the sanctimonious servant. Turning the pages, he discovers another entry that reads,
“An awful Sunday.....I wish my father were back again. Hindley is a detestable substitute—his conduct to Heathcliff is atrocious—H. and I are going to rebel—we took our initiatory step this evening.
"The initiatory step" taken by Catherine and Heathcliff is their tossing of the books that they were given to read after the three-hour sermon by Joseph. Catherine pitches into the dog kennel her volume of The Helmet of Salvation while Heathcliff kicks his edition of The Broad way to Destruction. For these acts of rebellion, Hindley, whom Cathy refers to as "the tyrant," jumped from his seat and seized Heathcliff by the collar and Cathy by the arm, hurling them into the backkitchen. In further rebellion, Cathy and Heathcliff, then, have run off across the moors. Upon their return, Hindley has banished Heathcliff from the company of the others, forbidding him to sit or eat with Cathy and himself, declaring that their father had been too lenient with the "vagabond."
Clearly, from her diary entries Cathy aligns herself with the brooding and wild spirited Heathcliff and rebels against old Joseph and her mean-spirited brother, Hindley.