Bellatrix awoke with a start, shaken from looking back on all those memories she had tried her hardest to forget. At least she had been spared the worst moment of her life. Only that didn't really do any good, as now she was remembering it anyways. Without being able to stop it her mind wandered back to the one memory she had hoped to have forgotten for ever. Now, in the dark underneath the Hogwarts castle it all came crashing back down onto her. Even though she could still see the darkness around her, she found herself in the hours before the big battle again, talking to Cissa in the short period of time the dark Lord had released her from the imperius so she „could witness with her full mind" the destruction she had brought upon „that filthy excuse for a school".
She remembered recognizing the look in her sisters eyes, the glazed, apathetic expression. She recognized it as it had been the look she'd seen in the mirror so often in the past years. Someone, probably Lucius, the man she had once loved, had placed Narcissa under the imperius curse. Bella could just picture it, her sweet little sister, fighting her husband, probably not even really putting in effort in, because after all, he was her love. Even when they were young Bellatrix had never understood how Cissa hadn't been sorted into Hufflepuff, she was they most loyal person she had ever met, and she would have quietly let herself be imperiused before hurting Lucius.
At that time she hadn't even tried to talk to her sister, everything she said would be reported, she knew. That way, she had just kissed her on the cheek and left.
Some hours later, the battle had been going on for a while, a tiny glimmer of hope, crushed again just a second later, to be replaced by fear worse then anything she'd felt before. When the dark Lord had fallen, for a moment, after his failed attempt to kill Harry Potter, in the forrest, she had felt the imperius lighten a little, and for a moment she thought he might be dead, she might be free. No such luck. He had arisen again and the curse around her had strengthened, becoming worse then it had been before. Only she had noticed something else.
When Voldemort had fallen Cissa, who apparently hadn't been in Lucius' grip after all, had shaken of her curse. Cissa had benn freed, the dark Lord had lost her, and he hadn't even noticed. The whole continuing battle Bella spent worrying about her sister, 'surely someone had noticed she was not on their side, surely she had been killed by now'. And then she had been forced to kill Molly Weasly, the only death by her hand in that battle, and in doing so she had robbed seven -no actually six- children of their mother, and Arthur of his wife.
That, she thought, was the thing that had finally broken her. Afterward she had been in a daze for the short rest of the battle, not even noticing anymore what he forced her to do. Only when it was all over and she had seen her sisters family, alive and alright, there had been a short moment of happiness. Then she had been thrown into the lake.