Kurama is their mutual attitudes, even if Yoko's is somewhat suppressed because a human belongs in a human world, so yeah, Yoko would probably survive if Shuichi does die, and they could split, but like you said I don't think Yoko is in any hurry to leave the guy. So you want Botan to permanently die if she's killed as a human? I'm trying to understand exactly what you see for her should anyone succeed in killing her.