the hero is a braindead retard... they have already killed the demon king and are very powerful, it doesn't change anything whether they die there or not. why would there not be peace and wars start again if the hero isn't dead? if the humans wanted to go to war they would either way. she said it herself that if they escape they would even probably not try to find them because they fear their power. in fact, by dying, she is letting all the corrupt ones in power do whatever they want without being restricted by powerful heroes. so, that bitch is making her friend die with her for no reason and increasing the chances of there not being peace. she's probably just a psychopath who wants to be with him forever and has already brainwashed him. I mean, just look at her face in her final moments, she looks like she's enjoying it more than looking like trying to comfort him