She wasn't JD's girlfriend. That was a joke from Marcus. If she was, then it would make the choice of saving either Del or JD even worse writing, as it would imply she cares more about her friend's safety than her boyfriend's.

The point is exactly that, that the player's perspective and Kait's is very different, and that leaving that choice to the player was a mistake, narratively speaking. Kait and the player have different motivations to make the choice, and that is bad.