It was true that Patience did not fully understand all the details of the deaths of their family. She knew that her brother had been killed by Greyback, that their parents had been killed by Death Eaters, but the reasoning behind all of it was hazy. She had a general idea that her parents had done something wrong, something to earn their deaths, because she knew, somehow, that the Death Eaters would not have simply killed them for no good reason. And her brother - well, werewolf attacks were something unto themselves, which did not always happen for a good reason, but she couldn't find it in her to resent Greyback very strongly. Nor did she hate the Death Eaters who had killed their parents.
Many of the other details, such as the choice Chastity had made to save her, were unknown to her. Perhaps the sick feeling was simply due to confusion, because there were puzzle pieces missing from her memory of that time. But she hadn't taken it as hard as Chastity, whose actions since then had made her a very different person than the one Patience remembered from before their brother's death.
It was certainly much nicer to remember Aldous alive than to try puzzling out all of the things that she didn't understand. She had plenty of memories of him, his wide-eyed wonder as he looked at the world. "I think he would have made a wonderful Ravenclaw," she said, fingertips running over the handle of her cup, the cool porcelain in contrast to the warmth of the rest of it. "Do you remember how he used to invent his own games? With cards, and pebbles, and anything he could get his hands on."