Dark Desire

Don't worry, she can't truly die. She's an undead, just like all the NPC's and the ashen one. There's a point in the game where you can give her eyes, for an alternate ending. You also get the option to reverse everything back to get the usual ending instead, so she asks you to kill her, to revert everything. She will respawn the next time the area is loaded, as she can't die. 

Nicer than twilight