She's not expecting him to be able to say everything here, but she also trusts him to be discreet about everything. Steve's a soldier, not a spy. But he's also pretty good at making plans, which Nat will freely admit. It's why she follows his lead, after all. She respects his abilities that much.

So when Steve lowers his voice, she leans in close to make it a bit easier for him. She puts her arm around him so that from an outsider's perspective it just looks like they're two friends embracing.

"I got that much. So, what's this about alternate universes?"

She steers the conversation away from the other stuff. For now.