Lilly is an original character who first appeared in Season 1 of Telltale Games' The Walking Dead. She is both a quick thinker, and a leader; she is also straight to the point regardless of how people react or feel about what she has to say. However, she does have a kinder side to her, and will appreciate others when they deserve it, but since her bosy and uptightness shows far often this is rare to occur.
At first glance, Lilly is quick to earn the dislike or disrespect from the group, particularly due to her association with Larry, her father, and her constant take on siding with him. For the better part of the episodes, Lilly assumes the role of the group's de-facto leader, probably out of the reason that nobody wants to take up the responsibility.
As Lilly has military experience (Air Force, specifically), she handles herself pretty well among the men and isn't afraid to speak her mind in order to protect her father and herself. Additionally, she is knowledgeable in survival tactics and firearms, which became a trait for good leadership. She even set up a training regimen for the adults in the group. In general, Lilly is rather bossy and possessive, having the need to control the group in a way that she sees fit. An interesting point to note however, is that when Larry starts acting out in a fit of rage, she is quick to act as a pacifist and attempts to calm him down, to no avail at times. This shows that unlike her father, she does not bear the similar bitterness and resentment that he has for everyone else, although she does have a temper not to be reckoned with.
Should Lee try to get in favor with her, the game will reveal a softer side of Lilly that is in fact, a warm, considerate and polite lady who is unsure about her capabilities as the group's leader. Repeated conversations with her will show that Lilly tries to apologize to Lee on behalf of her father, stating that while everything Larry does is ridiculous, it is in the intention of protecting her and affirms her ground on siding with her father. When caught in conflict with Kenny, she reveals that she tried to see things from his point of view as a father and husband, yet finds no reason to support his decision, as it puts everyone else at risk. In fact, she confides Lee at times by asking him if her decision was right as a leader.
Despite having to prioritize her father, between Kenny and herself, she is more interested in overall group's welfare, and thus prioritizes everyone equally whereas Kenny seems to prioritize his family beforehand rather than anyone else.
At the end, Lilly's personality and responses are entirely dependent on how Lee treats her throughout the story. Simply put, if Lee tries to get in favor of her, they will get a glimpse of Lilly's softer side. Vice versa, if they go against her, she will continue to put up a tough persona and fight for what she thinks is best for the group. As of Episode 2 onward, Lee's relationship between her and Kenny will be put to a test.
Robins Air Force Base
Lilly, is the daughter of an army man and was stationed at Robins Air Force Base where she held a desk job. She is used to dealing with pushy military men and immediately takes charge in tough situations. During a conversation with the St. John family while waiting for dinner, she reveals that she had seen action during her service. While incredibly strong-willed, she will always submit to her dad, Larry, a grizzled old man with a history of heart problems.
"Episode 1: A New Day"
She is first seen while saving Lee, Clementine, Kenny, Katjaa, and Duck from a walker attack. She takes them into a drug store where her group has set up camp. However, when rescued, her father, Larry, started yelling at Kenny and Lee for putting them in danger and claims that Duck is bitten and needs to be thrown out. Lee then needs to make a decision on whether to side with Kenny or Larry. As the group argues, Larry suddenly has a sudden heart problem, causing him to faint and collapse to the floor. Lilly takes care of him and asks Lee to get pills out of the back part of the pharmacy which is still locked. Later, Lee comes to talk to her and apologizes for what happened earlier, which she somewhat forgives him for. She continues caring for her father while Lee, Carley and Glenn are at the motel. When they get back, Lee attains the keys and they finally go and get the pills. However, when they open the locked pharmacy door, the security alarm goes off, attracting many walkers. They get the pills, treat Larry, and figure out a plan to escape. Lilly, Larry, and Glenn protect Kenny and his family while they get the truck, while Lee, Doug, and Carley hold down the shop. After they get the truck, Lilly sends her Dad back to get everyone else. However, he punches Lee in the face, but Kenny arrives and saves Lee. Later that day, they camp at the motel where Lilly talks to Lee and Kenny on how she thinks they will be okay at the motel, when suddenly the power shuts off.
"Episode 2: Starved for Help"
During the 3 month gap between Episode 1 and 2, Lilly, Lee, and presumably the other survivors trained in the use of firearms in Lilly's "intensive training". During an argument, Lilly will force Lee to hand out four pieces of food to the starving individuals. After this task is complete she will tell you, with a soft tone of voice, that it's not easy doing what she does. Lee tells her he doesn't envy her.
If given a piece of food she will reject it at first (depending on what the player said during the previous argument,) but accept it without much force. She will comment that it doesn't change anything after. However, if you chose to side with Lilly when she and Kenny were arguing, she will gladly accept the piece of food that you give her.
"Episode 3: Long Road Ahead"
After Kenny and Lee return from the Pharmacy, she is either content or enraged with the amount of supplies scavenged. When Kenny suggests leaving in the RV, she scolds him (and Lee, depending if he helped to kill Larry) about how she trusts them. Kenny insists on his plan, and she becomes enraged once again, mentioning stolen supplies. After everyone leaves, Lee comes back to ask about what she meant by "stolen supplies", and she states that someone has been stealing them. She asks Lee to look around for clues. When he comes back with the medical supplies that were hidden outside, she realizes someone is selling them out, and takes it very personally, believing it to be a crime bordering on indirect murder, and asks Lee to help her round up the group so the traitor can be exposed.
But before that can happen, she looks outside and finds the Save-Lot's Bandits holding the group hostage. She grabs a rifle, ordering Lee to distract the bandits, and jumps outside her window. Lee's distraction works, and she takes the bandits by surprise, showing great skill at sniping several of them, as Lee gets everyone on the RV. When walkers arrive, she barely manages to enter the RV, knowing the Motel is lost. With the motel gone, she loses it and begins to question who the traitor is. She believes it is either Ben or Carley/Doug. When the RV runs into a walker in the road, and they have to pull over for an emergency stop, the confrontation comes to a head, as she tries pressuring Ben and Carley/Doug into pointing fingers at each other, threatening to leave one of them behind. In the end shes shoots Carley/Doug. She can either be left behind for dead or taken prisoner. If she is kept prisoner the she will later steal the RV from the group when they stop. After that, she is never seen again for the rest of the series.
"Episode 5: No Time Left"
If Lilly was left behind in Episode 3, the Stranger will criticize Lee because he abandoned a "defenseless, grieving woman" clearly referring to Lilly.