Slytherin Marauders

Severus is astonished to find that a girl was abandoned who lived in Hogwarts, and even more so once he hears her name. He recognized her, & knows she won't recognize him, but what will he do when she wants to know more about her past through him? What will he do when she turns to him for comfort and guidance? He'll get confused during that, but even more so when she falls in love?