If I was not mistaken in the translation, Cathy invited Sophia and Liam to visit. But it was said that there is an important conversation with Liam.
That is, the emphasis was on the fact that the conversation would take place with Liam, probably in the presence of Sophia.
Did I understand correctly what should happen in the evening, or was I mistaken with the translation?
You are right!
I didn't noticed but the dialogues for the invitation are quite similar but in the case of Aiden's path (only Liam is there) she says
while with Sophia in the room she says
So, "you" Vs "you guys". Now this could be just a simple transcription error. I'm not a native speaker either, the first sentence can still mean "you" as in "both of you", and she just used "you" as plural without "guys" because Sophia was not there. But I let the native speakers to jump in and give an interpretation to such subtleness.
The invitation in any case is for both of them and even Liam says "We'll drop by".
I'm leaning more for the simplest explanation, they will talk about the same thing regardless the route (GW, Aiden), even because both of them will be there and if they wanted to talk only to him she would have explicitly invited only him.
IMO, what will probably change in the event are some dialogues or scene according to the route and the fact that Liam peeked at Cathy in the dressing room.
But it's just a guess like any other at this point, we are a bit in the dark with this event.
For reference the extract of the dialogues here