This is my first attempt at a fanfic so please go easy on me.
Not canon, obviously, more a little 'what if.' We know almost nothing about Professor Sinistra from the books so I took a little licence with her and with the delicious Professor Snape.
Disclaimer: I own nothing, characters etc are the property of J.K. Rowling. This is a fanfic written purely for entertainment and not for gain.
The room was stark, almost sterile. The man who had lived in these chambers for more than ten years had not left the slightest mark of his own personality on them. There were no personal items, she had searched every drawer and every cupboard. There were a few books, he had kept most of them in his office but there were one or two here that were rare and quite old. She tied them up with string from a ball that she had found in one of the excessively neat drawers. In all the years that she had known him, she had never set foot in his rooms; he needed his space, his solitude. When he needed her, he came to her. She always welcomed him and let him seek what ease he could find in her arms. She walked through into the bedroom. Still nothing, this room might have had any resident or none, there was still no trace of him. She was tired, she had not slept since they had brought back his body. Even now she could not openly declare herself, could not weep over him as she wanted to. She had not exposed him to gossip or ridicule when he was alive and she would not do it now. For seven, no eight years, they had carried on a secret relationship under the noses of all of their colleagues and not one had suspected.
Her grief and her condition caught up with her and she first sat down on the bed then laid down, burying her face in his pillow. It still smelled of him and it evoked memories both sweet and bitter; the nights when he would come to her tower after her students had gone back to their beds, when he made love to her by starlight and moonlight, his anger and his black moods, the sweet little notes that he sometimes passed her under the table at meals when they sat next to each other but never spoke. She remembered the daisy chain he had made for her in secret and brought to her on midsummer's eve, five years ago. She felt a tiny lump in the pillow that shifted when she prodded it. Her questing fingers found a small bundle of cloth. She pulled it out and was surprised to recognise one of her own handkerchiefs. It was folded very carefully; having unwrapped it, she simply sat and stared for a little while, transfixed by what she had discovered. Here was a lock of her hair (the fluffy, silver-blonde curl was unmistakable) tied with a red ribbon, a part of the very daisy chain she had just been thinking about, withered and dry but still recognisable and a button from one of her old dresses. He had kept these things, so secretly that even she had no idea, and slept on them, dreamed on them. She wept for a little while, holding on to his pillow as if it could save her from drowning. As if it could stop the sky from falling.
After a while, the storm passed and she wiped her eyes. She sat up and looked around the room once more. There was nothing else that was his. She tucked the little bundle from the pillow into her pocket and stood up carefully. It was time to go. She picked up the collection of books and walked out of the door leaving the rooms unlocked and unwarded for the first time in over a decade.
The carriage was waiting to take her to the station, they had asked, then begged her to stay; the school had already lost too many teachers. But she could not, even if she wanted to. She would begin to show soon and then there would be questions. Even now after it was all finally over and his true sacrifice had been recognised, she would not burden their child with the reputation, the history and the sheer misfortune of his father's name.