Imagine having been a Hufflepuff who grew close to Sirius while still at school. Years after parting your ways, you finally meet again at Grimmauld Place.
As the kids tried to eavesdrop on the conversation behind the closed door, someone else walked into Grimmauld Place. It was a woman, late twenties or maybe early thirties. As she walked down the hallway, she looked up and smiled at the teenagers holding one end of the ear telephone.