I took this a bit differently. If she and her children had been raped and then just witnessed her husband, whom we should assume was a kind and good man in the regular world, reduced to a killing machine, then I sort of understand her choice. I'm not sure I would see much point in living in such a violent world, or in subjecting my children to it. I took it as less that she was scared of Abe and more that she was broken by how much he has had to change to live in the ZA. I think she gave up, as opposed to running from him, and I kind of can't blame her.