Johanna gives him a look of disbelief, mainly because she wants to know where in the world there aren't structured alliances. "People always gravitate one way or another," she points out, seeing as that's just how the world works, as far as she's concerned. "It's pretty much us versus them. The 'them', in this case, being the people who trapped us here."

Because no matter how irritated Johanna might be with some of the people here, most of her ire is reserved for the ones trapping them. If it turns out to be the Capitol, then all that anger can be stored up and shared together, conveniently.