Well. Steph wasn't expecting that - Kalinda doesn't seem like the touchy-feely type - but she's nothing if not adaptable and so she moves her hand to the small of Kalinda's back in response. (It'd feel weird not to do anything.)

And it takes her a moment to respond, unsure how Kalinda meant that statement to be taken, "I've found some upsides." Seems like a safe enough response.