If you look at Aries at the end, it's virtually (if not exactly) like she was at the very beginning of the game when she was kneeling by some place (praying?) with little green balls of... shinyness... coming out of someplace in Midgar. My interpritation of that was to show that Aries had had a premonision of all the things to come, showing she knew everything that was going to happen. That's why she wasn't afraid, because she knew she was going to die, and that there was nothing she could do about it, but she also knew that the world would be saved. Does that make sense?