I also chose to sacrifice Chloe. At the time, it felt like a weighty decision. In reality, I would have let the town burn to save someone I really loved. But logically it was the right thing to do. In any case, Chloe was all but begging me to let her die in order to save the town. It would have been far tougher if she had made the point that she didn't want to die, as I think most people would.
I'm not convinced that her selflessness so much represents a character development as a situation where the writers wanted you to make a certain choice, or to wrap up her ending neatly. It's interesting that the denouement for sacrificing Chloe was a lot longer than the other one.
Once the decision was made, though, the story deflated to a disappointing funeral scene in which, far from being struck down by the horror of what she has been through, Max merely looks like a young person who has Learned An Important Lesson In Life.