Even after Amycus had told her not to, Alecto had turned herself in with the hopes of freeing him; he would definitely be able to live without her, but he was her everything, and if she had to live without him, she might as well be the one suffering the consequences of her jealousy. She'd had no choice but to try everything she could to free him, even if it meant being naive enough to believe the Ministry would actually let him go if she turned herself in. But even that small chance was better than just letting him taking the fall for her mistake.
And since returning home, she feared his anger and retreated into herself and her room, coming out only fix dinner, in an attempt to let Amycus calm down and not give him further reason to be upset with her.
On the eve of the new year, Alecto wasn't sleeping, but she might as well have been. She was curled up in a chair, reading a book she cared nothing about when her brother knocked on the door, asking for entrance. Did he expect her to refuse him? Perhaps he had had enough time to calm himself. Alecto hoped so. She was tired of avoiding him, of walking on eggshells.
"They're open," she called to him, still in her chair. She hardly ever locked her doors because if Amycus really wanted in, he'd get in. That and as long as he wasn't upset with her, she wouldn't deny him anything.