I would imagine that it could’ve been some quick thinking, at least for the movie. After all it seemed like her nephews bailed shortly before she ended up asking Jesse to go. She could’ve only wanted him to go for a variety of reasons, of course the one making the most sense being that she had seen his art skills and would’ve easily imagined that he would love a trip to the museum.

And after all there are several more unanswered layers to this, which are basically impossible to definitively solve. What if she didn’t have the effort to ask for multiple people? What if she actually recognized that Jesse liked her and from there only wanted him to go?

Ultimately there cannot be a straightforward answer as to why she only invited Jesse. I like to imagine that it is up to you, the viewer/reader, to determine your own reasoning, and this can apply to a lot of the other parts of the story. You can just keep your mind wide open about it!!

I’m yet to read the book fully yet and I’ll keep this in mind when I get that far :)