Some have speculated that Patricia could be that character.
Patricia has described to Sophia that her agreement with Carl that she can fool around so long as she does nt allow her pussy to be fucked. Now allowing for the fact that Patricia might not be a perfect witness, my view is that until we learn something to the contrary, we have to accept this statement as true.
Therefore although Patricia might be a shameless flirt and complete tease, we have to assume that Patricia would nt cheat on Carl with anyone, be it Brydon? at the nightclub, Jason and Haru at the museum or even Dylan. I just think at the moment Patricia wants Sophia to loosen up to be her partner in crime as she fools around.
But, as several others have previously suggested, if Sophia goes too far in her corruption, that Patricia could be the one to deflect her back before Sophia passes the point of no return.
Of course speaking personally I would currently be more than happy to see both Sophia and Patricia screwing around left, right and centre, well at least until the point in the story where this has serious consequences nearer the end of the game. But for now I can forget that as being far. far in the future and just look forward to as many hot and erotic scenes as possible, hopefully soon leading to sexual acts and then to actual full sex.