You are Snape's daughter. It was an evening with an unknown woman after Lilly Potter died. Snape was sad and sought comfort with another woman. Nine months later, you were born. Your mother sent a letter to Snape telling him he had a daughter, but after the letter, he heard nothing more from you or your mother. Your mother went into hiding. Your mother is also a witch. But she has problems. She is addicted to drugs and works as a prostitute. You have an incredibly difficult childhood and find comfort in books. Snape searches for you for years. And when you are 18, he finds you. You have social anxiety disorder and severe depression. He takes you to Hogwarts and tries to be the father you deserve.