Why does Odile feel that she knows the children's librarian even before she meets her?

Odile feels like she knows the children's librarian, Muriel Joubert, even before she meets her. Odile has seen Muriel's signature on the cards of books she checks out to read for herself. When they meet, she discovers that Muriel is a young girl her age, and as she surmised they have the same reading tastes.