I like the Mrs as not safe nor necessarily helpful (the 2D planet is one of the very few things from the middle of the book I actually remember! and liked in a horrible way!) but I also like Meg making an active choice against advice to do a stupidly dangerous thing rather than being dumped helpfully on a planet to do a stupidly dangerous thing by other people. Meg doesn't have to do what anyone says! They're not her dad!

(I would also have liked to have more of pointlessly contrary Meg other places in the film too, but I'll take what I can get.)