Faith looks at the kid just as he's striking a deal with Marcus. She twists her mouth in momentary distaste at the idea of just joining in. It's not that she didn't want to, it's just... well... OK, she doesn't want to. Not really. But Owen's easy acceptance of the deal is like a challenge, like he's lapping imaginary wings and going 'buck-uck!' at her.
Finally, she walks to the trio, and says, in her usual direct fashion, slaps her hand down on top of Nightfall's. Probably a little too hard. Unintentionnaly, I'm sure. "F**k this, I'm in." She looks at where Spartan should be. "Shit. Let's f**king hurry this, Alphonse's already gone through."