You know what every trio of dudes needs? A kick-butt, smart, non-dude member to make it four people instead of three. (Hey, even the Three Musketeers was actually comprised of four members.)
And Van is just the girl to round out the sausage-fest of rebellious teen tech geniuses. She's got opinions and isn't afraid to share 'em. Van's resistance to Marcus's ideas gives us another point of view on what goes down post bridge explosion. In fact, Van makes most of the great ideas that inspire Marcus. The plan to change how "normal" encryption looked for people using the internet comes from her musings.
But then things get sticky with her and the rest of the group.
Van walks away from Marcus because she can't watch him suffer. And we see her point. Her parents fled from North Korea, so they know about harsh governments; Van doesn't want to watch Marcus become a victim of something he can't actually beat.
So she disappears for most of the middle of the book, even though Marcus still thinks about her:
I hadn't spoken to Van in weeks, and those weeks felt like months. We used to talk every day. (14.44)
We get why she's not part of the web of trust party, but when she comes through for Marcus at the end, we see what real friendship means to both her and Marcus.
Did we say friendship? Whoops. That should have been l-o-v-e. That's right, one of the reasons Van is so upset with Marcus is that she has a long-standing crush on him. And Darryl has a long-standing crush on her. And Marcus is now dating Ange, who goes to the same all-girls Catholic school as Van—so things are complicated, to say the least.
Like with Darryl, at the end of the book there's still some distance between Van and Marcus…but that's what happens when l'amour is on the table. Still, she's definitely someone we'd want on our team.