Heathcliff is Catherine’s one true love. This is evident from the way she talks about him, even after she is married to Edgar. She says things like, “I’m Heathcliff–Heathcliff! Who are you? You’re a Linton; and you’d best not tell me much!” (page 49). This quote shows that Catherine still feels connected to Heathcliff and that she still loves him, even after marrying Edgar.
Catherine also confides in Heathcliff—she tells him her deepest secrets. For example, when she tells him about her engagement to Edgar and how she is afraid of losing her identity by marrying someone else: “But now I’ve told you all my private affairs—and so much too! Next time we’ll go on with some interesting talk about our books” (page 128).
Catherine is drawn back to Heathcliff no matter how hard she tries to push him away. This is evident when she rejects his advances at first but then goes back to him.