It didn't really have to go for Nightingale. The joke could have gone for Ritsuka's known resistance to poisoning. Serenity or Asclepius could have shown up for that. I found it amusing that multiple users guessed Nightingale and were right
Well, it's a cannon that if ya refuse to get nursed by Nightingale, getting into hell feels like heaven. When she hears someone in small pain or having a spec on dust in yar hand, she won't stop chasing ya even in the depths of the earth just to get rid of that spec of dust.
Heck, even Bersekers, who usually acts like suicide bombers, are terrified by her XD