The answer to the first question is easy enough: Steph is the one who pulls open the door, having checked the camera feed she's set up (Bats). She's got a few hours between one job and the next, so she's at home for a little while, at least.

"Kanaya, hey. I hope you didn't have too much trouble finding the place," Her smile is easy and warm, as she opens the door wider and steps back to let Kanaya in; Saul gave her a heads up about the potential visit, so she's not surprised.