Being told she was not the one to kill Tobias brought such a mixture of emotions, Eileen wasn't even sure she was capable of processing them all. The wand slid out of her hands and onto the floor, rolling slightly and she put her face in her now free hands. Shame, guilt, relief, anger - all bubbling up underneath the surface. Shame, guilt, and anger because she should have been the one to kill him, the task of getting rid of Tobias shouldn't have had to fall to her son. Relief, because she didn't have to, and he was well and truly gone. Shame again for feeling relieved.
"Oh, Sevvy." The tears spilled over. She hadn't properly cried and certainly hadn't ever done it in front of her son, in a very long time. Of course, longer than she even felt it had been, but Eileen had never been one to let her son see how desperately bad the situation was. She tried, though not to great affect, to shield him from it as best she could. "Twenty years. I - I'm so sorry, Severus, I - it should never have had to be you." After a few more moments, it dawned on her.
"The - that was, wasn't that just - " She remembered, just yesterday it felt, was the twentieth. Was it not? She looked up at Severus, the confusion still written so painfully all over her face. "But why, Severus? Why did you do it? And - why don't I remember the last twenty years?" Of course, she was starting to gather that she had likely been dead too even if he didn't flat out say it.