There are two main reasons Estella does not return Pip’s affection. One, she is incapable of feeling affection. Two, she does have brotherly affection for him, but she wants to use her romantic affection to get back at Miss Havisham.
Estella plainly tells Pip that she cannot love him because...
she does not have the ability to love. Miss Havisham raised her to be cold and heartless, and have no feelings. She tells him she has no heart.
“Oh! I have a heart to be stabbed in or shot in, I have no doubt,” said Estella, “and, of course, if it ceased to beat I should cease to be. But you know what I mean. I have no softness there, no—sympathy—sentiment—nonsense.” (ch 29, p. 162)
It is actually out of a sort of affection that she tells him this. She is trying to spare his feelings. In her own way, she does care for him. What she really means is that she has no ability to LOVE romantically. She cannot be in love with him. She thinks of him as a brother, because they grew up together. She also has no desire to marry for love. Miss Havisham raised her to get revenge on men, and she intends to kill two birds with one stone. She will offend all of the gentlemen suitors by marrying the dolt Drummle, and she will affend Miss Havisham by not involving her.
Miss Havisham is upset with how Estella turns out. She wants a daughter she can feel affection for, or who will at least feel affection for her. She accuses Estella of being cold toward her, which is unacceptable, and Estella accuses her of hypocrisy.
“You should know,” said Estella. “I am what you have made me. Take all the praise, take all the blame; take all the success, take all the failure; in short, take me.” (ch 38, p. 206)
Estella cannot love Miss Havisham. She informs her that she has her love, as she has been taught to love, and no more. Estella blames Miss Havisham for the kind of life she had, and the kind of person she has become.
It is one of the great ironies of the book that Miss Havisham's creation turns against her, and Miss Havisham finds herself wanting love, familial love, and not able to get it because of how she has treated those close to her.
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