I don't completely buy the idea of her being the "everyman" character as there's a lot
going on in this movie that isn't explained to us by her. In fact the only thing her "everyman" character prompts an explanation for is what an Einstein-Rosen Bridge is. Otherwise she's just a clueless, self-minded, person rolling her eyes in the background and occasionally calling her boss out as a criminal.
"Everyman" characters serve much more of a purpose in explaining the plot to the audience. As I mentioned above, Winston in "Ghostbusters" is a great
example of an "everyman" character. Our three heroes are all scientists with doctorates in specialized fields of study who designed
this equipment and study this stuff. Sure, some things get explained to Peter (a doctorate in psychology rather than the more obscure things everyone else is specialized in) but Winston holds no doctorate and some things are explained to him, vicariously getting explained to the audience.
Darcy? Not really much. "Everyman" characters can also give the audience someone to latch onto in a movie with fantastic characters we can't
easily relate to. I'm not sure Darcy fits this role either because I doubt many audience memebers are easily going to relate to a selfish, snarky, twenty-something girl.
I think her character isn't our "Everyman" and more our "lame comic relief."