This is basically Carol flirting. Teasing is her way of trying to connect with people. It’s similar to Thomas but different. Her style is much more mean than Thomas. To the point that it doesn’t read like flirting, but she’s playing. The more Thomas reacts in this sort of serious way the more she wants to bat at him and see what happens. Thomas is more playfully inappropriate when he does the same thing. It’s such a minor difference but it’s what makes up their styles. The subject Thomas brought up is sort of naughty and Carol wants to see what Thomas’s reactions to her responses will be. SHe probably doesn’t even consciously realize she’s doing it. It’s just how all the things that made her Carol shaped her to act. In combination with her internal makeup.
I dunno. I do know that I can’t identify it IRL. On the page here it’s obvious because I know these characters intimately, but for people I’m not familiar with I can’t read it at all. Probably because my default is to assume all other humans are waiting to attack me, or make fun of me, or do some other negative thing. That’s how the world trained me.