I thought I wasn't sure, only seeing the "X likes you a bit more" in the status box, however, in the following example as you can see, I haven't had much interaction with the lady except for sending her a message "thinking of you" once when she got suggested as a partner for a threesome by one of my girlfriends
View attachment 3854063
So it can't have been a prior instance of a threesome.
By the way, since I have multiple girlfriends and understand that this is not considered "cheating", nor is a threesome cheating for the involved girl - however is a threesome encounter with girlfriend X and "stranger" Y considered cheating by other girlfriend Z - after all you had sex with Y which you shouldn't?
And also: why does she have an attraction towards me of 100? She's not even "Love at first sight"?
Edit: while we're on the subject of threesomes, I accidentally took the virginity of one of the girls during a different threesome. First: props that the game notices that. However, it was not mentioned in text thus easily missable (the opinion boost gave it away), also - but that's probably a headache to imüplement - I think that maybe virgins shouldn't start with threesomes with (relative) strangers.
2nd Edit: as for the amateur contest: I just noticed that the "open at night" law hasn't been implemented in my city yet. So they can hold a contest, but since it is at night, they needed to close for that reason. Maybe you can make the laws dependant so this cannot happen? At least that should be easier than have the AI check for it when deciding on holding a contest.