Rachel was kind of like...he's related to Ginny? I don't think she noticed him enough in her second year to pick up on all the differences (and besides, Ginny was a little quieter then). But now she's just like, huh, interesting.
She looked none too impressed by his little speech. She had to try very hard not to make some sort of incredulous sound at his explanation for Azkaban, because, really. She's not an idiot. Rachel was also sort of confused about what he was saying at the end of his spiel. So are they claiming to just be reintegrating muggleborns into the muggle world?
Rach also thought it was rich that he called the muggle world mundane, because he seems pretty stiff and boring to her.