easy they didn't change it it was never said she was anything, they seem to be giving her a back story and before you say anything about that she's not the only one Mei Yin now has a brother, a brother that has never been mentioned I see no difference in this. All of this will be before their life on the Ark they die and wake on the Ark with their old memories. All they are is adding to the story fleshing it out.