Gith'yanki do not have quite the same psychology as the RL people around you.
Lae'zel may not exist in the real world, but I do. Belonging to a different culture doesn't grant anyone the right to threaten their loved ones with death. Even "killing machines" can show kindness and care to those they truly value. I don't understand why people enjoy this kind of toxicity, it's more of a sadistic femdom fetish than a healthy expression of love.
As for Shadowheart, I'm not sure, because I always visit Nightsong's jail without her. The dialogue feels poorly written, offering only two choices: "I'll kill you" or "Do whatever you want". The option "Please do it for me" never convinces her, which reinforces my point that either the writers don't understand true loyalty, or relationship points don't reflect the strength of a bond. As I understand it, 100 approval should mean "I would die for you" not "You're allowed to invite me to dinner", right?