I can't remember Chloe smiling either but she has her "tender" moments. Such as when she told Jack if he needed someone to talk to, she'd be there. Funniest darn scene!
I remember that--toward the end of last season. Jack looked at her: "What?" Hahaha
And this season when Chloe reunited with Jack, she threw her arms around him and gave him a big hug. Jack wasn't expecting that :)