@Yatogami Firstly he once went back to save her so it's only right that her repay the favor or she could have at least told the others that she saw him then and there but no she waited untilthey had full escape to bring up the fact that she saw him. Yes they probably wouldn't have gone back but she could have at least tried. Secondly if he tried to help his friend he would have died as well.
~xoxo♡