Honestly, she's noticed that Duo seems to be looking rather good for someone who's been out there fighting. And sure, it's easy to imagine the healers are to thank for that, but Alice is actually more generous than that (maybe a little too generous, honestly) and assumes it must also just be because of Duo's skills. No matter how weirdly lighthearted his attitude seems to be about things when he speaks, he's seemed capable enough.

Even when he's saying this kind of stuff with a laugh and a grin. He may just be joking, but Alice's tone is as serious as ever.

(Granted, could her tone even be anything but that?)

"That line of thinking has rather severe implications about the train. If we aren't at the very least on the good side of these conflicts, we're little more than a bunch of mercenaries who aren't even getting paid."