In Ch.15 Pip learns from Miss Havisham that Estella has been sent "abroad... educating for a lady; far out of reach; prettier than ever; admired by all who see her." Finally, Miss Havisham with "malignant enjoyment" dismisses him gloatingly "do you feel that you have lost her?" Pip returns home completely disgusted with his present situation to discover that his sister has been knocked senseless by an unknown assailant.
Towards the end of Ch.16, Biddy moves into Pip's house after the death of her great-aunt. In Pip's own words she "became a blessing to the household" because Pip's sister has now become an invalid who needs some one to take care of her. In Ch.17, Pip praises Biddy by saying "she managed our whole domestic life, and wonderfully too." Its from then on that a certain intimacy develops between Pip and Biddy.
In Ch.17 one Sunday afternoon he has a heart to heart conversation with Biddy which reveals the inner conflict and mental torment which Pip was experiencing because of his infatuation for Estella. He openly confesses to Biddy that if had not met Estella he would have become a partner to Joe in the forge after the formal completion of his apprenticeship and that "you and I and Joe would have wanted nothing then .... I should have been good enough for you.
In his heart of heart he knows fully well that Biddy is the ideal soul mate and wife for him, but he is completely overwhelmed by his foolish infatuation for Estella. Pip describes his pathetic situation thus:
"how could I, a poor dazed village lad, avoid that wonderful inconsistency into which the best and wisest of men fall every day?"
Biddy although she sympathizes with Pip's plight is non judgmental and tells him that he has to decide for himself whom he should choose for a life partner. Biddy unlike Estella "was never insulting, or capricious" and Pip wonders, "how could it be, then, that I did not like her [Biddy] much the better of the two [Biddy and Estella]?"
Finally, Pip asks her plainly "I wish you could put me right...If I could only get myself to fall in love with you... that would be the thing for me" To which Biddy replies very bluntly, "but you never will you see."
Dickens very graphically describes for us a teenager's infatuation for a very attractive girl [Estella] and how it blinds him to the worth of a gem of a girl like Biddy. In Ch.30 Pip very categorically tells his friend Herbert who advises him to "detach" himself from Estella that it would be impossible for him to do so: "you can't detach yourself?" No. Impossible!"
Biddy is kind to Pip and doesnt judge him like Estella does, but Pip still favors Estella for her beauty.