I think you're misreading the story. It's not an argument in favor of irrationality, it's a horror story. The catch is that it's a good horror story, directed at the rationalist community. Like most good horror stories, it plays off a specific fear of its audience.

You may be immune to the lingering dread created by looking at all those foolish happy people around you and wondering if maybe you are the one doing something wrong. Or the fear that even if you act as rationally as you can, you could still box yourself into a trap you won't be able to think your way back out of. But quite a few of your peers are not so immune. I know I'm not, and that story managed to scare me pretty effectively.

The protagonist isn't an ideal rationalist, and the story isn't trying to assert that this is what the ideal rationalist does. Instead, the protagonist is an adolescent proto-rationalist, of a type many of us are familiar with, with her social instincts sucking her into a trap that a lot of us can understand well enough to dread.

And so there's a reason she thinks and acts like a Hollywood stereotype of an intelligent person is that, especially when they're just barely at the age of being able to really think at all. Where do you think Hollywood got the idea for the stereotype in the first place?

I submit that the reason so many of the average people think intelligent people act that way is because they lose social contact with the geniuses in high school, which is when they do think and act like that.

For a lot of the smartest people, being socially functional is a learned skill that comes late and not easily.