It's hard not to notice other humans; there are so few of them, and with Steph's wariness ramped up to eleven by the situation, she's even more watchful of her surroundings.

So, other human, and the other human here watching her, which could mean any variety of things. The most likely reason is the same one she notices him, so it doesn't raise her hackles like it normally would, and instead of walking away, she walks over. There's a bag in her hand, folded fabric inside it, suggesting she's been out for at least a little while.

"How long?" She saw him glare at one of the salespeople, sees how he's dressed and how he holds himself, and figures that B.A isn't going to be one for small talk. So she cuts straight to the point; how long has he been on Tu Vishan?

The fact he smells like gunpowder doesn't escape her notice.