I don't get it. How come when in the Fall Chapter at the university when that survivor was attacking Joel did Ellie not help out? She usually comes behind and stabs them with her switchblade or shoots them. It seemed out of character for her to not doing anything.
She was likely still a bit shocked/disheartened to learn that the Fireflies had left. The fact that her and Joel had come all that way, only to have to travel even further, would be pretty draining emotionally. Also, running into the Cannibal scavenging party was kind of a surprise for the two of them.