Well, Karlach death does remind me somewhat of Aerith, back in 1997...
You don't have to like it, the game designer doesn't have to fix it either.
I do think all characters should be okay with Karlach in Poly, because they understand she's got weeks to live at best and could die at any time. Indulge her before time is up.
Man really said "Forget the plot holes, where's my orgy" LOL