[Mm, he's smart. Always too smart. But she doesn't want him to take first blood, here, and if she waits too long, he'll have enough energy to run away. So she thinks she can spin this right.]

Uhm, I think it was the thing w-with the microwave beeping in your bed. But you didn't switch the m-mustard. I don't even think we have mustard. It was ketchup, or it w-wouldn't have looked the same.

[C'mon, Sans, switching mustard wouldn't have been a good prank. But she has one that's even better.]

Here, uhm, I can ask one I think.

[And just like that, the facade is dropped; her smile grins too wide, head titled too high. Let her take the judgement reveal this time, buddy.]

Where w-were you when I took in corpses and made abominations in my lab? Lazing around in Snowdin, p-perhaps?