You and Draco were hiding, one day she was in Draco's room, and the two of them in their underwear were lying together talking, until they heard a knock on the door.

They put on some clothes and she hides behind the door, and when Draco opens it, he leaves a hand covering her mouth, and it was Blaise Zabini, Draco's best friend and he says

Blaise: "Draco, the rest of the guys there are calling you, come on bro"

Draco: "It's not possible now" He says while covering her mouth hidden