The likelihood that I’m not joking is zero almost everywhere. Added to that, I think marriage is a quaint custom which one can joke endlessly about – from a distance.

I was thinking of lil’ bro may be wearing a wedding ring as a ward spell against horned demonesses (or other females he doesn’t know). But demoness could wear an engagement ring, which could provide her emotional energy.

But yes, it looks demoness is being demonessish out of pure spite/old habit.