She's mad about it for more than being dead. Spite's a big motivator.

"Nice monsters?" she blurts, before she can consider what she's saying. She almost follows up with I've never heard of that, except, maybe she has. She wonders if the nomes count.

She does, of course, notice the body language, something she's learned to read fairly well in a place where hardly anyone talked. She's pretty sure Frisk's death wasn't an accident.