While Biddy loves Pip, his feelings for her are platonic. He sees her as a sister figure (a much better one than his biological sister ever was). Pip does not realize until it is too late that Biddy has been a true friend to him.
Because of Biddy's love for Pip, she desires to see him accomplish his goals, but she is apprehensive about his going to London to become a gentlemen because she knows that she will most likely lose him forever. She is a simple character, without Pip's extravagant tastes, and realizes that London society will only whet Pip's appetite for the "finer" things and people in life.
Having spent time with Pip in her great-aunt's school, Biddy becomes childhood friends with Pip, especially because both are orphans and are emotionally neglected in their homes. Then, when Mrs. Joe is debilitated, Biddy comes to stay and attend Mrs. Joe. While living with the Gargerys, Pip, who still considers her a friend and confidant, confides in Biddy that he wishes to becomes a gentleman, but Biddy feels his motives are wrong.
One night while they sit by the fire, Pip notices how pretty Biddy has become, as well as how efficiently she manages her household chores. The thought occurs to him that he could have a nice life with her if he were not so consumed with his desire to become a gentleman. As he tells her about Estella's insults and his desire to prove that he is not "coarse and common," Biddy listens, and finally advises him.
"Because if it is to spite her," Biddy pursued, "I should think--but you know best--that might be better and more independently done by caring nothing for her words. And if it is to gain her over, I should think--but you know best--she was not worth gaining over."
Biddy is obviously aware of the shallowness and egoism of Estella and concludes that Pip will be hurt by her if he pursues her, knowing that the girl has no heart.