
What the hell did they do to her? She's batshit crazy.

It's probably meant to be seen as the result of her personal bad karma (from being nasty even without black magic) joining with her blackmagic karma (which has finally caught up with her) and with the karma of refusing her shaman fate (even though it was never taken to this degree, I have indeed read other Korean stories where chosen future shaman "candidates" would suddenly get sick if they got chosen but didn't perform the ritual to officially "accept and receive the divine spirit" that would give them their shaman powers). Moreover, she'd already been generating additional bad karma completely on her own, all this time, by continuing to act like a b--- even AFTER she dodged her fate, and even without the aid of black magic: how she has kept baiting, mistreating and harassing people every day (and not just Sera) even without black magic (like blondie and blondie's female admirers, for one... AND, drugging the 2nd ML probably earned her even more bad karma points). It's crazy because it's like, this b--- didn't fully ever realize the position she was in, and instead of keeping a low profile to avoid making it worse, she thought that if she could get away with it (and without karma catching up to her) once, then maybe she could get away with it again, and then again, and then again,,, ad infinitum... and that's how she increased her already super bad karma by acting all nasty all on her own, even without the hekp of black magic. And now that, all that bad karma has finally been joined by the bad karma from both rejecting her fate as a shaman, and from using dark magic to shift the harmful consequences of that onto someone else, it's finally enough to ruin her spiritual and mental health, which will sooner or later mess up her physical health, too.
Glenn, I want a turn