It's probably gen b/c Lily's brother James had stolen the map from their father's desk and maybe Lily stole it from James. The map would think that it was still Lily Evans. I hope that explains any confusion.
An unflattering map of a Victorian woman's heart. “The Open Country of Woman’s Heart: Exhibiting its internal communications, and the facilities and dangers to Travellers therein” (D. Kellogg & Co. of Hartford, Connecticut,