Probably Carley/Doug were destined to die by Lilly's hand the moment they wrote the script for this game. Even so, I'm still sadden by Carley's death and there is two more episodes to go to change things. Whether TTG have any further plans and surprises or perhaps the storm swirling over her death might get them to alter the story a bit... we can hope.
However, I doubt she can be brought back but I don't mind being wrong here. What I would like to see at least is Carley being mentioned in a few conversations. Lee using her gun. If possible, Lee thinking of her in dream or getting knocked out (or falling on his head will do) and hallucinating. What do you think?