Did her grin just get wider? Why yes, it somehow did, as she cackles when Heiji is done speaking and asks, "'Collaring'? Is that like a slap on the wrist you humans do to criminals when they're caught for sure and handed their guilty verdict after a trial or...?"

However, a slight raise of brow on her part becomes obvious as she considers the words "let them go" that had fallen from the male's lips. So she then asks, "Do you even know what kind of torture this guy has probably subjected many people to? Let's assume he already has a body count over twenty, are you going to be on board of 'letting him free to go' then?"

To Terezi, this was completely confounding-- sure she knew the human race was less destructive and harsh than hers but hearing how light they could be on criminals still didn't exactly do well with her.