Option 2: A perfumer's nose for scents -> The passage explicitly states: "It was a gift Ashlyn had since she was twelve, like a perfumer's nose—the ability to sense the echoes attached to certain inanimate objects, especially books." This is a direct comparison made in the text.
Hence, Option 2: A perfumer's nose for scents -> The author uses this specific metaphor to describe Ashlyn's supernatural ability to pick up emotional vibrations and echoes from books she touches. Just as a perfumer can detect subtle notes and nuances in scents, Ashlyn can detect the emotional residue left by previous owners of books, such as fear, worry, and sadness -> correct