Why did Silas ask Miss Lupescu to serve as Bod's temporary guardian?

In The Graveyard Book by Neil Gaiman, Silas is the "guardian" of Bod, a young boy who lives in a graveyard. Silas protects and educates Bod and also brings him food. In chapter 3, Silas explains, "I need to obtain some information. In order to do that, I have to travel." Bod enjoys the company of Silas, and he is sad that Silas has to leave. Since he must go, Silas asks Miss Lupescu to serve as Bod's guardian in his absence.
At first, Bod is not at all fond of Miss Lupescu. He finds her to be strict and boring, and worst of all, he dislikes the food she brings him. Silas brings food that "mostly came in packets, purchased from the kind of places that sold food late at night and asked no questions." Miss Lupescu brings food that is healthier, but to Bod, it is "slimy and unfamiliar."
In spite of the food, Bod eventually grows to like and appreciate Miss Lupescu. He learns the value of the lessons she teaches him, especially the lessons on how to ask for help in every language. Miss Lupescu, who is actually a werewolf, saves Bod's life.