He doesn't really doubt it, even if he has a hard time imagining someone being that selfless. But Hamunaptra is a pile of shit and death traps.

Cassian notes her discomfort in the skirt, another bullet point on his list of things he's observing about her and Bodhi both. He sits back and crosses his arms. "Sleep while you can."

He should do the same, but he's definitely going to check out the rest of the ship first, as well as the rest of the passengers.