We first meet Miss Lupescu when Silas has to leave the graveyard for a while. She's the person Silas found to be Bod's guardian while he's away. At first she seems like the worst kind of substitute teacher. She gives Bod lessons, but they're all super boring. She's extremely strict and demands that he pay attention. And she makes Bod eat nasty food. She's the kind of substitute teacher who might cancel your class pizza party because you fell asleep during her snooze-worthy class, and then feed you beetroot-barley-stew-soup because pizza isn't healthy.
Even though she seems like the substitute teacher from Hell, she turns out to be a werewolf who saves Bod from Hell. That's right, when the ghouls drag Bod into Hell, it's Miss Lupescu who rescues him.
Miss Lupescu, Substitute Guardian
As we said, Miss Lupescu and Bod don't start out the best of friends. Why? Because of her bossy ways and her icky food. Make that seriously icky food: “dumplings swimming in lard; thick reddish purple soup with a lump of sour cream in it; cold boiled potatoes; cold garlic-heavy sausages […]” (3.68). That's a big change from the food Silas gets for Bod, which “mostly came in packets, purchased from the kind of places that sold food at night and asked no questions” (3.38).
Miss Lupescu isn't only feeding Bod’s body with home-cooked, high-nutrition (well, except for the lard) food, she's also teaching him all the discipline and practical knowledge he’s lacking. She tells him about all the kinds of "people" in the world, including ghouls and Hounds of God. She also teaches him “ways to call for help in every language in the world” (3.68).
Teaching Bod to cry for help in Night-Gaunt (the language of the night-gaunts, of course) soon helps him escape Hell and the ghouls. But teaching him to call for help in every language of the world will help him wherever he goes, not just Hell. And if he knows how to call for help, he’ll also recognize when someone else calls for it too. Since he seems meant for a life of heroism, this is a good thing all around.
Once Bod realizes that Miss Lupescu's lessons actually are useful in his life, he becomes an enthusiastic student, drinking up all the knowledge she puts before him. Bod and Miss Lupescu seem to become friends, and she even takes him to a football game.
Miss Lupescu, Hound of God
Earlier we called Miss Lupescu a werewolf. Maybe we shouldn’t have done that, though. She might not like it. After Bod finally realizes that she and her big grey dog are the same, she writes him a note of explanation:
Those that men call Werewolves or Lycanthropes call themselves The Hounds of God, as they claim their transformation is a gift from their creator, and they repay the gift with their tenacity, for they will pursue an evildoer to the very gates of Hell. (3.262)
From this we can gather some important facts. First of all, Miss Lupescu is religious, and she believes in God. This doesn’t tell us anything about her religion, or what her idea of God is like. Second, she suggests that all werewolves are Hounds of God. Unlike in a lot of other fantasy books, werewolves in The Graveyard Book aren't evil.
Like Silas, Miss Lupescu is a member of the Honor Guard (more on that in Silas’s section) and she dies battling the Jacks. She seems to be an important part of the fulfillment of the prophecy that if Bod reached adulthood, all the Jacks would be destroyed. But beyond that, she presents a strong female role model for Bod, a woman he can look up to and respect.