Carly was destined to die from the moment in which Doug died in episone one. And Doug was destined to die from the moment in which Carly died in episode one too. The designers simply had a "problem" since episode one, because they had to design situations in that Carly/Doug would fit equally. They couldn't keep designing two versions of the same scenes every time, and I'm sure this is the reason why Carly/Doug went back to the motel with Ben in most part of episode two. Carly/Doug couldn't be made important anymore, since they could be dead from episode one. The death of one of them in episode one in fact sets the grim fate of the surviving other later, and Telltale tried its best to postpone the inevitable moment as long as they could.
I am noticing the sexism in some games since I have started playing them with my wife, what is a great experience to have together. She called my atention to the clothes of the female characters, for example, and to some subtle trends that are revealed in the context or in the plots. I'm happy that she helped me to perceive this, because now I think that the games could be made so much better if we all make an effort to understand and analyze the problem like adults. :)