To a large extent, I don't think revising the original Portal ending was necessary. GLADoS seems a little... ambiguous on the whole concept of individuality with regard to test subjects. They're all vat-grown. The insults and threats all seem selected to *statistically* get reactions but without much regard for personal case. ANY human would be "you killed me", in the same way that "you were abandoned by your parents" (remember the vats?) or "you're fat", regardless of the actuality of the situation. Chells are all plentiful, replaceable, interchangeable, and all GLADoS's personal nemesis.