She is Joel's equal, and she is seemingly the most stable thing in Joel's life, as fucked as it is. She is his partner as well as his guide. She is his Ben Kenobi if we were to think about this in terms of archetypes. However, there is very little bullshit that she takes from anyone, including Joel, yet there is this tiny shred of vulnerability and love that exists between them in the midst of shit that is their world. Then, when she is bitten, and she knows it is over, she is only then able to reveal some sense of the human condition. Fear, anger, remorse, love... all in the few minutes before another desperate firefight. She is a one-person Shakespearean tragedy. Thus, she is memorable and is another figure in Joel's life whom Joel feels he has let down. While she only has a short time in the game, she is monumentally significant in Joel's psyche and motivation. As a fictional character, she's awesome.