"My mother's a witch like me, and witches in general are keenly aware of human partner mortality. As long as Ranata likes Charlie, she can't bear to leave him, because then he'd die at some point without her - I don't even have my afterlife figured out yet so I can't reassure her on that - and she'd never have the chance to change her mind. I don't have this problem because I have pretty much always considered the correct solution to be to research immortality. Which I successfully did even before getting minted."