Yes it's a bug with the conflict events that was the issue where they would trigger despite not actually being in a relationship with that character.
This has been fixed in the latest version and will be in the next public version.
recently tried a new playthrough on 37.96
kate's line died off (idk if i maybe failed something but events stopped happening) but i kept getting the messages about her & the internal conflict of *cough* dating basically everyone *cough*
two things, first:
i like kate & want to see more of her route, so i'd guess some others might too & it's not all that clear (possibly intentionally?) when the cut-off for getting onto that route is (which in itself is fine imo), but it took me quite a bit of reload-go-forward-reload-try again to get there, which wasn't all that satisfying bc it's hard to see if you've left a route aside from simply never getting another event proc... maybe a 'relationships' screen would solve that? even if it didn't have anything beyond a tick/route lost indication it'd be helpful for people trying to find & stay on specific routes :)
the other:
it'd be a lot of work but... if someone depraved (like me) tries to go every route at once, perhaps some new options/dialogue/thoughts for someone not into monogamy? poly people do exist & it might be interesting to add character's reactions & storylines to that player option?
love the game, great artwork & lovely writing. keep it up!