The social event was invite only and to supernaturals,
Yes and it was mentioned a couple of times that the area was a hotbed for the supernatural and the magical, they were attracted to the place like flies.
If one of them is working in a tech store then it stands to reason they will also work as waitresses, bar staff, street cleaners etc because the are is full of the supernatural.
The only weird sight was Becki with I because she's apparently an average human and she was there.
A cat turning up with an invite belonging to someone else is weird.
A resident of a supernatural town turning up to a supernatural gala is probably one of the most normal things in the game.