Although Catherine desires Edgar because of the money and position he offers her, which she thinks she can use to better the life of Heathcliff, the text also suggests their relationship grows from abuse, her power over him and his willingness to give her that. “You’ve made me afraid and ashamed of you,” Edgar tells Catherine after she boxes his ears in Chapter VIII, yet he does not leave her. “I saw the quarrel had merely effected a closer intimacy,” Nelly tells us, adding “he possessed the power to depart as much as a cat possesses the power to leave a mouse half killed, or a bird half eaten.” The irony here is that Catherine is the cat and Edgar the mouse or bird. Their relationship grows from her desire to and ability to wield power over him (“eat” him) and his willingness to acquiesce to that. Indeed, her passion for Heathcliff is so strong because he is the inverse of Edgar. Catherine could never dominate Heathcliff: with him she meets her match, he is as powerful as she, and in that way is her “soul mate.”
Catherine is attracted to Edgar Linton's lifestyle. Thrushcross Grange symbolizes a comfortable idyllic world. Edgar can provide security to Catherine, something Heathcliff cannot. I believe Catherine did love Edgar, but without passion which made Heathcliff so irresistable.
Catherine marries Edgar because he is a part of the right social class. She finds him "handsome, and pleasant to be with". When Nellie says her reasons for marrying him are superficial, Catherine tells her she plans on using Edgar's money to help Heathcliff rise in the class system. For five months, they seem to be a happy couple, but after Heathcliff returns, Catherine cannot hide how happy she is to see him. Edgar sees she is still attracted to Heathcliff and asks Catherine to choose between Heathcliff and him. She refuses to honor that request. She later blames Edgar and Heathcliff for breaking her heart because she could not choose between her love for Heathcliff and the life that Edgar could give her. Edgar was the only way that Catherine could be a part of the upper class, and although I think she cared about him, she never loved him. She used him and then blamed him for her unhappiness.