In fact, back then she wasn't acting out a plan with Zachary Armstrong; her illness was real, and Zachary Armstrong had deceived her too, making her truly believe she was not long for this world.
But actually, although her condition was the same as Max's, because it was discovered early, surgery was on time, so after surgery and some time recuperating, she slowly recovered.
However, Zachary Armstrong, worried that she would know the truth and not be able to fool Shane Winchester, kept her in the dark. In doing so, he made Shane Winchester truly believe she was dead, allowing her to have a genuinely peaceful life with Mason Wright.
After finding out the truth, she had no way to blame him because back then, it was she who had made up her mind to leave Shane Winchester, and Zachary Armstrong was merely helping her make it more thorough.
