I hope I'm wrong, but I think Nami is a wildcard and she's even more damaged than Nika. Despite all her goofiness, I absolutely agree that this is a façade and partly her optimistic nature. And we see the real Nami after the MC's date with Bella, when she suddenly has a breakdown and hugs MC, trying to childishly hold him beside. Of course, she quickly pulls herself together and even jokes, romance and fisting... But even the MC understands that she is hurt.
Nami is not kidding when she complains that again some blonde bitch will steal the MC and she will drink herself into a coma at the MC's wedding.
Fuckin' devs love to mess with the emotions of players and confuse a throuple with a triangle. So I'm sure at some point there will definitely be a choice: Nami or Bella, and then everything will go downhill.