Falleen and pheromones encounter
Perhaps 1 success means they resist, but passively so. They are left endeared but not willing to follow. They might see no reason to alert the others, and just pass it off as a normal thing to have someone try to do.
2 successes or greater might mean they resist and are able to alert the other players to an attempt having been made, if they so choose.
I have no idea who is in your party, but when dealing with attraction powers I handle it like this: if a character would be attracted, they are. That means just because a character is male != attraction to a female Falleen, nor does it preclude the possibility that a male character would be influenced by a male Falleen's pheromones.
How well do you know the player(s) concerned?
I think you could get around this by letting the player respond to the situation but don't alert them with a narrative check until
they ask
for one.
How well known are the Falleen to your players both in the game and their knowledge of Star Wars?
Ideally you could avoid revealing they're Falleen until one player responds by willingly allowing their character to go off with her/him alone and it doesn't necessarily mean outside the building just the next room.
Then introduce that narrative roll, simply being out of sight of the other players and pointedly noting that unless they have a reason to suspect anything they shouldn't be reacting to something that as far as they know is purely the other PC's problem now if he is able to get a warning off or another PC decides to spoil that player's fun well that's another entirely different kettle of fish...
PS: Would the Falleen's pheromones effect more than one character at a time? Because in the latter situation mentioned above what would stop having
both PCs
getting into trouble?
How well do you know the player(s) concerned?
Very well... I might start with the narration and see how far I get until the player starts to push back... The player in question doesn't know about the Falleen, when they started to ask why they felt so compelled to follow the NPC I was going to give them a knowledge check to see if they knew about the Falleen and if they were successful offer boost dice on the charm check.