This discussion may contain spoilers!
Christa, that is. I'd put money on it.
Offing Omid served a very useful narrative purpose for Christa. It left her bitter and I think gave her a bit of inner turmoil. On the one hand, I think she has for many months been telling herself that Clem is just a little girl and shouldn't be blamed for what happened. On the other, I suspect some irrational part of her is raging at Clem, blames her for leaving her gun on the counter, and generally holds her at fault for what happened to Omid. You could detect an undertone of resentment in her treatment of Clem all through their scene together which I believe stems from this.
All of that is great fodder for interesting character development, for both Clem and Christa.
Except if Christa is just straight up dead, in which case the whole beginning of the episode turns from setting up an interesting exploration of character into Telltale just clearing up irritating loose ends from Season 1 so they can get into straight Season 2 stuff. Which is lazy and boring writing.
So yeah. Christa is probably alive. There's still too much she can add to the story for her to be dead.