There's a flash of something like surprise, or concern, or both, muddying up her expression when he shows off his arm. But he stops and maybe it surprises her a little more that he does himself first. Makes her think about pointing out both that's she's not positive he's not himself and just out of his gord, under a spell, something, or that there are a number of ways he could be holding that form magically that silver wouldn't give a damn for showing.

But the list of people in the universe who knew they could use Dean against her was incredibly slim, like two sets of hands at most slim, if that many anymore, and at this point she was probably sure even Dean wasn't aware of that fact anymore. More things that were her fault, and her weight to bear.

She took the knife, with something of a frown, looking at it in her hand, and saying, "You'd think you'd have had enough of my blood already," as she shifted hands, so that her wand was in her left and she could use the knife in her right. Meaning more that it was dripped all over the room already, but it wasn't about blood and she knew that as much now as she ever had as a kid, before the magic. Jo cut a thin line into her left forearm, without flinching as she watched herself.

She held out her arm and let him see it, too.

Pale skin staying pale, and blood beading up as jewel red there as the rest that dripped and stained elsewhere.