Rei :

Rei is not facing death willingly because she is strong, but because life doesn't mean anything to her. This isn't mere pessimism, but a death-wish, like a dark gloom of death that surrounds her. Her self-esteem, self worth is very low, she doesn't communicate with her classmates and if she would be asked to die for the cause ... she would.
That makes her an impersonation of Binah, as Binah's illusion is death.She lives a life of sorrow, the vision of Binah, she is always quiet, the virtue of Binah.
When Rei II sacrificed her life in favour of Shinji, she disobeyed a direct order, further, when Rei III rejected Gendo in favour of Shinji in the process of Third Impact, she freed herself from her fatalism and "It doesn't matter" attitude, and in doing so, she evolved into a living being whose life does matter.