He'd actually gotten the idea she might be interested in him before now, because he's not quite as dumb as he looks, but he's been pretending to ignore it until tonight. He's pretty sure, since she keeps sliding into his lap, that she's already noticed he's interested.
Connor's trying to fight it, and she's driving him up the wall, but he also has centuries of practice and control. Connor kisses back, but tries to very gently ease her back to the couch beside him in the process.