The main issue is, that you are not allowed to try fixing her by the game. If Gondians tell me "sorry we can't fix her, because her heart wil explode during the surgery", if Mizora tells me "sorry I cannot help you, because hells order abc123" forbids me to help you" then it will be completely fine. But isn't it strange, that if I play as a good character and romance Karlach, I not able to speak with them about the fix? I can speak with all npcs in the game, very often about nonsense (in a good way), but I'm not allowed to speak about the most important thing for my Tav with npcs directly connected to hell, Zariel and infernal engines?
