Why does Nelly feel Catherine is misguided about her duties as a wife? How does Catherine's response demomstrate the differences in her feelings for edgar and heathcliff?

In the kitchen Cathy came to talk to Nelly (neither of them knew Heathcliff was in the room, sitting behind the settle). Cathy said she was unhappy, that Edgar had asked her to marry him, and she had accepted. She asked Nelly what she should have answered. Nelly asked her if and why she loved Edgar; she said she did for a variety of material reasons: "he will be rich, and I shall like to be the greatest woman in the neighborhood, and I shall be proud of such a husband" (78). Nelly disapproved, and Cathy admitted that she was sure she was wrong: she had had a dream in which she went to heaven and was unhappy there because she missed Wuthering Heights.

"I have no more business to marry Edgar Linton than I have to be in heaven; and if the wicked man in there had not brought Heathcliff so low, I shouldn't have thought of it. It would degrade me to marry Heathcliff, now; so he shall never know how I love him; and that, not because he's handsome, Nelly, but because he's more myself than I am. Whatever our souls are made of, his and mine are the same, and Linton's is as different as a moonbeam from lightening, or frost from fire." (81)

Nelly feels that she is misguided because Catherine doesn't want to be with edgar for love, but for his money and status. Catherine tells Nelly that If Edgarn Linton demand that she forsake Heathcliff that she would not marry him because she loves Heathcliff and doesnt't want to live a life without him. In Catherines response she states that her feelings for Edgar may change so she might actually love him for the right reasons someday but that her feelings for Heathcliff will always remain the same.