Initially, The Last of Us showrunners wanted to pay considerable attention to Tess and her life during the early days of the mass outbreak.
According to Craig Mazin and Neil Druckmann, several scenes were supposed to reveal more about Tess, as well as her son and husband, who were infected at the very beginning of the pandemic. The heroine had to personally kill her husband, but did not have the strength to kill her son, instead locking him in the basement, where he presumably turned into a clicker. Later, Tess tells this story to Joel and Ellie.
According to the show’s creators, Tess was thus contrasted with Joel: even after losing the two people closest to her, she still remained a strong, hopeful woman, while Joel seemed like a gloomy pessimist in comparison.