the waif worked for jaqen h'ghar. You were the vermin to this girl. Or you were named vermin? Meh. You were a rat to her. She wanted you dead. No reason truly. But you were also a vermin to jaquen. Wasn't truly a reason either. But you didn't care. But the waif truly is someone you had to be afraid up. She could stab you. And she did. You were in healing at the moment. But it was best you stay hidden.