Both Ron and Ginny were making vague references to somebody that apparently didn't have a name. At first, when Ron was the only one talking about 'she', Hermione had felt extremely jealous. Who was this woman that Ron was so eager to see? Then, Ginny seemed to know the woman too and that heightened Hermione's curiosity.
"Who is this person?" Hermione asked, narrowing her eyes in suspicion. "Is it somebody I know?"