An orphan who teaches Pip to read and who takes care of Mrs. Joe after the attack, Biddy is a kind and thoughtful young woman who has romantic feelings for Pip but ends up marrying Joe Gargery.
For someone as quiet and unassuming as Biddy is, she’s really amassed quite the long list of accomplishments. Think about it: she somehow actually learns to read, write, and do arithmetic at that horrible excuse for a school, Wopsle; then she manages to teach it to Pip; then, she not only steps in and totally takes over running the Gargery house and taking care of Mrs. Joe, but she actually manages to decipher that weird letter-T-hammer-thing that Mrs. Joe is constantly drawing as Orlick. Even Pip, never the sharpest tool in the shed when other people are concerned, somehow realizes that, "She managed our whole domestic life, and wonderfully too […] (17.5).
In fact, Pip is quite curious at how Biddy manages to be so awesome:
"How do you manage, Biddy," said I, "to learn everything that I learn, and always to keep up with me? […] when I come in from the forge of a night, anyone can see me turning to at it. But you never turn to at it, Biddy."
"I suppose I must catch it like a cough," said Biddy, quietly; and went on with her sewing.
I began to think her rather an extraordinary girl. For I called to mind now, that she was equally accomplished in the terms of our trade, and the names of our different sorts of work, and our various tools. In short, whatever I knew, Biddy knew. Theoretically, she was already as good a blacksmith as I, or better. (17.5-13)
Pip is floored when he sees that everything that comes through painful effort to him comes super-easily to his friend. And indeed, Biddy is totally one of Dickens’s patented exemplars of female competence, most of whom follow this template of being sad nothings that rise to the occasion and demonstrate their awesome skills (like, say, Esther in Bleak House or Amy Dorrit in Little Dorrit).
So does this level of expertise help Biddy or hurt her? Shmoop will throw out the idea that part of the reason she and Pip never get together is that he feel like he’s always completing with her, and so his default reaction to seeing her do stuff is to try to immediately put her down, so she remains beneath him.
For example, right after he realizes all that stuff we just quoted, he busts in with this gem of a backhanded insult: "You are one of those, Biddy," said I, "who make the most of every chance. You never had a chance before you came here, and see how improved you are!" (17.14). Nice one, bozo—way to make your one friend in the world cry because you’re so insecure.
What do you mean, who’s Jiminy Cricket? Why, he was Pinocchio’s externalized conscience! Well, in the movie anyway. In the original Pinocchio Jiminy started trying to make the wooden puppet feel bad for misbehaving and was immediately squished. Which is actually pretty fitting, because that’s about what happens to Biddy every time she pipes up with some advice or other to try to help guide Pip in his dealings with Estella—he basically squashes her. Even when he’s secretly agreeing with what she is saying.
There’s a great moment early on, when Pip shows up to talk to Biddy about how he’s met Estella and now wants to be fancy-pants for her. Check out how everything Biddy says is exactly what Pip is already thinking… and how uncomfortable he is when she just externalizes his interior monologue:
"I never shall or can be comfortable—or anything but miserable—there, Biddy!—unless I can lead a very different sort of life from the life I lead now."
"That's a pity!" said Biddy, shaking her head with a sorrowful air.
Now, I too had so often thought it a pity, that, in the singular kind of quarrel with myself which I was always carrying on, I was half inclined to shed tears of vexation and distress when Biddy gave utterance to her sentiment and my own. […]
[…]
"The beautiful young lady at Miss Havisham's, and she's more beautiful than anybody ever was, and I admire her dreadfully, and I want to be a gentleman on her account." […]
"Do you want to be a gentleman, to spite her or to gain her over? […] 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."
Exactly what I myself had thought, many times. Exactly what was perfectly manifest to me at the moment. (17.29-41)
Biddy is the voice of reason, moderation, and rationality here. As well as the voice of morality, confirming that yeah, Estella is kind of a huge jerk to call Pip out on his background. But at the same time, as soon as she feels Pip resisting her wisdom, she totally hightails it out of there, and just gives Pip a shoulder to cry on rather than the stern talking-to that he clearly actually needs.
So while we admire Biddy for being right all the time, we kind of wish she would buck up, too, and tell Pip what's really up. But alas, that would be a different novel.