Rei, the 18th angel (its my assumption that if Rei had appeared on her own like Kaworu did, she would be identified solely as the 18th angel, instead of all of the humanity) The show identifies humanity (Lilim) as the 18th Angel, not Rei. Therefore, Rei is not the 18th Angel -- Lili...
Something that's been bugging me for a while, if Kaworu, the 17th angel and Rei, the 18th angel (its my assumption that if Rei had appeared on her own like Kaworu did, she would be identified solely as the 18th angel, instead of all of the humanity) have the souls of Adam, the 1st angel ...