Catherine says that Heathcliff and Edgar have broken her heart as she's dying because . . .they have. Wuthering Heights serves as a romantic template that is used to this day in modern work such as The Twilight Saga, The Vampire Diaries, and Legands of the Fall.
She is conflicted by her love of bad boy Heathcliff whom Bronte uses to show that the cliche "reformed rakes make the best husbands" . . .because he never reforms and never shows more than a glimmer of redemption, he's one of the orignal bad boys in literature and her love of Edgar who offers her stability, kindness, and good social standing. Catherine herself is also a template because she has aspects in her character that can relate to both Heathcliff and Edgar. She marries Edgar and loves him in her own way, but she never stops loving Heathcliff and he never stops torturing her about it, even on her deathbed. She dies in childbirth and is buried on the moors between both of them.