Just A Groupie Not A Threat

The most remarkable thing about that moment is that when Ellie watches him beating a man to death, she is activated. Earlier in the episode when Sarah sees him killing this old woman who is infected, who he has to kill, she cries. Ellie doesn’t cry. Ellie likes it. She likes the idea of somebody defending her like that, and she likes the idea of that guy being punished.  

This is where you begin to see the problem, but also the deliciousness of the pairing. These two are meant to be together… but look out.  

And then Dina goes "Oh Ellie, they should be terrified of you." and that's when it hits her.

Basically, Dina's kiss hits her sooner than the realization itself.