Katniss is cautiously optimistic about Steph. Very, very cautiously, because Katniss is a bundle of paranoia wrapped in PTSD, but there's something about Steph and the way she greeted Katniss and has spoken to her since that makes her think she'd be better as an ally. She's still thinking of the turtle as being the Games, so 'ally' is about the extent she's willing to push that relationship right now, but she knows she'll need the help of other people to help her while she's here, and Steph is one of those people that her gut tells her it wouldn't be terrible to be around.