how do you write a story where the protagonist dies?

not one where the protagonist is fighting you every step of the way- not one where she is begging you to spare her life. I feel like that's easier, because you just set fate in motion, and hey, for the story you want, you can't interfere. it was always going to end like this. like yes I'm mourning you, but the laws of this world I've built dictate that your death is inevitable. Sorry. It will be over soon. Then we can rest.

but what do you do when your protagonist wants to die?

not because of suicidal ideation, because that, too, would be easier to deal with. you show her that life is still worth living. you show her kindness, and love, and even if she still constantly wants to die at least she can see that she might need to work on that, and you can at least promise her that things will be okay. it got better for me, so it's really just common decency to make sure it gets better for you.

but what if your protagonist has lived too long? What if there isn't any getting better because this is better, this is as good as it's going to get, and to live is to repeat a thousand years of illness and stasis?

The win state's long since been reached. She's loved and lost and longs only to go home to the place her mother and her mother's mother and her grandmother's mother has died.

how cruel am I, then, that my first instinct is to deny her?