Lars' brother Gus is quite hostile to the idea of buying into Lars' delusion while his wife is more supportive of the idea. This, of course, causes tension between the two of them. The screenwriter, Nancy Oliver, has cleverly intuited that how well or poorly a bizarre behavior by a family member is handled by the family (and the community), makes a huge difference to healing. She also strongly implies that the behavior is the attempt at healing. This film would be an excellent teaching aid in mental health recovery programs.
Doctor: What we call mental illness, isn't always just an illness ... It can be a communication, it can be a way of work something out. Gus: Fantastic. When will be over? Doctor: When he doesn't need it anymore Karin: How can we help? Doctor: Go along with it
Gus: -- Oh no. No that's... No no... No I mean... pretend that she is real? I'm not gonna do that, I mean I can't. I'm just not gonna do it Doctor: She is real.
Gus: -Well... Doctor: She's right out there
Gus: -- Right, I get that I'm just not gonna... You know, I'm just not gonna I'm not gonna do it, so... Doctor: You won't be able to change his mind anyway Bianca's in town for a reason.
Gus: -- Right, but... but ... Doctor: It's not really a choice. Gus: Then we'll do it, whatever it takes.