@electro_neanderthal lol, he fell asleep later because he was further away and started hearing the song later. She then stopped her song to buff herself, thus delaying it further.
Also, the powers in this world have been shown to be much more of a soft power system than hard, meaning there's leeway in how they work. Its not that weird to be able to resist a little longer than others. I think you just need to pay more attention.