Hermione Jean Granger had a secret, or at least to her knowledge it was a secret. But I suppose one could say it isn't a secret if two people know and although to her credit Hermione didn't know that anyone else knew her most closely kept secret someone did. Night after night Hermione does something in the privacy of her highly warded bed. She draws the curtains closed and prays for her strength and her ability to keep her secret from driving her mad.
But what was this secret? Had she done something wrong, or made some sort of mistake? Had she made a wizards pact, or joined dark forces, something worse perhaps?? Had she lost a friend or family member, or maybe was it a lie? The truth was so much harder to explain but really it was quite simple when you boiled it down ad looked deep inside. She had feelings for someone who could never love her back, someone she could never be with, and the fact was that Hermione had been falling in love with Severus Snape for months.
Harry and Ron both saw him as the "Greasy Old Bat" and all of the students seemed to find him frustrating at best (Slytherins) or hated him at worst (Gryffindors), but if she were to tell the truth, Hermione saw something different. It is fair to say she was fascinated by the man, drawn to something about him. His very presence sent shivers through her core. While it is true she worked hard in all of her courses, potions was different. Hermione worked twice as hard to have praise fall from his lips.
Oh and those lips, she had so many fantasies about those lips. She couldn't imagine the disgust from her two best friends if they knew she dreamed about all the things those lips could do for her, or if they realized just how much of a whore the witch really was. To her dismay Severus was the only wizard she had ever felt any attraction to, but the night before her 17th birthday she couldn't help but be disappointed it looked like she would never have the love life every girl dreams of. But Hermione's fate is written in the stars, and prophetically whispered as an end to this wretched war, but if I spoiled all those secrets now it wouldn't be any fun would it?
Hermione sits on her bed, one hour before the day everything changes, thinking about all the things about Severus she knew she would never find with someone else, and she makes a decision, at 1 am Miss Granger was going to the Mirror of Erised and looking into it to see if Severus was her hearts truest desire. If it was she was going to do something to ease her pain, because she couldn't live like this forever.
She was a lot of things but she was not a hopeless romantic. People didn't just fall in love, especially not student and teacher. It was improper and she was far from improper. He would never just fall for her, and he especially would never simply bend her over his desk and shag her brains out like she so wanted him to do. With 20 minutes to one she decides to relieve some tension, the fun way.