Once, I had this idea (between books 6 and 7) that Snape had many good reasons for killing Dumbledore (namely protecting Malfoy) and he wrote this in a letter to an illigitimate daughter named Drella. Her mother was from America and was on an internship exchange program to the ministry of magic and Snape was in a weird place at the time. She finally told him about Drella around about the time Drella graduated Ilvermorny a fully fledged witch. This is sorta how i imagined her. #HarryPotter