I believe she is hearing something, but it's not knocks and whistles.
It's a voice that keeps telling her : "You are still a virgin ! You are still a virgin ! You are still a virgin ! You are still a virgin ! You are still a virgin ! You are still a virgin ! You are still a virgin ! You are still a virgin ! You are still a virgin !You are still a virgin ! You are still a virgin ! You are still a virgin ! You are still a virgin ! You are still a virgin ! You are still a virgin ! You are still a virgin ! You are still a virgin ! You are still a virgin ! ..."