Long before the apocalypse, the Flores family had a tradition of service to the Abigails, a prominent business family living in Valle de Guadalupe. Celia served the Abigails as the family housekeeper, and took care of the Abigail heir, Thomas, who lost his birth mother in childhood. They formed a mother-son like relationship, and Thomas also befriended Celia's own son Luis. After they grow up, Luis continued the tradition by serving Thomas as his personal assistant.
During a flashback of Victor Strand, Celia seems to be still working for Thomas shortly before the apocalypse. During Victor's vacation at Thomas' villa, Celia served drinks to the couple, and covered Thomas' chest with his shirt to prevent him getting sunburn.
During a conversation between Luis and Nick, Luis mentioned that his mother currently resides in the Baja safe-house. Although Nick considers this as the confirmation of the safe-house's safety, Luis came up with tricky responses that "his mother could survive anywhere, especially in this world" and "Death is the start of a new life", albeit with confidence.
She is seen in a flashback serving Thomas and Victor drinks while at the estate.
She is in charge of the estate and leads a belief that the Infected are not dead but in the next stage of life. She poisoned a church congregation when they decide to leave.
When the group to Thomas’s gated estate where Celia, Luis’s mother, greets them. Strand informs her that Luis is dead. “He’s one of them now,” Strand says. “Then he’ll find his way back,” she replies.
In the kitchen, Nick tells Celia that Luis asked for her when he died. Celia calmly explains that the dead have always walked amongst them. “The only difference is now we can see them,” she says. Madison overhears their conversation and later warns Celia that Nick is impressionable.
Daniel gazes at photos of the dead posted at an outdoor shrine. He notices an owl carved into a tree trunk, similar to Luis’s medallion. Celia posts a photo of Luis and explains that Luis’s death does not faze her because he was not shot in the head.
When Daniel finds the zombies in her wine cellar, he confronts Celia about it. She explains that they are all family members of people who work on the estate. As she prepares two communion wafers, Daniel realizes that she killed the parishioners with poisoned wafers. “They were killed by you,” she corrects, then urges him to make peace with his dead.
Celia brings the wafers to Strand and Thomas and commends Strand for deciding to die with Thomas. She leaves the room and locks it.
Nick finds Celia drinking wine in the courtyard. “They’re not really dead, are they?” he asks. She shakes her head and says the Infected are simply “what comes next.”
When Thomas is shot to prevent reanimation, she slaps Victor and calls him a liar. Celia forbids Strand from burying Thomas and attacks Strand when he declares that Thomas wasn’t her son. Nick manages to bring the fight to a standstill and she chastise Strand for allowing Nick to speak for him. Celia orders Strand and those he brought along with him to leave by the next sunset.
Nick appears leading an infected Luis to Celia after venturing outside the estate, masked by Infected blood. Celia invites Nick to stay at the estate. He convinces her to allow his family to stay with him, but she insists that Strand must leave.
Celia delivers a eulogy beside Thomas’s grave. After the ceremony, Celia tells Strand that it's time for him to leave as the sun is almost down.
Ofelia demands to see Daniel, but Celia says he’s too dangerous due to his recent attack on an employee. Later, Celia brings food to Daniel, who is tied up in a storage room, and urges him to seek forgiveness from his Dead. Daniel hears Griselda’s voice. After Celia leaves, Griselda’s ghost appears before him.
Madison implores Celia to let Strand stay. Celia refuses and tells Madison that she must learn to accept the Infected just like Nick does. Madison asks Celia to help her understand. Celia takes Madison to the cellar and enters the cell to show Madison all of her infected “children.” She tells her that they're safe with her because others would deemed them monsters and try to destroy them. Madison closes the gate, locking Celia in. They stare at each other unfazed. Celia then looks at the zombie horde beginning to make their way towards her.
Madison uses Celia as an example when explaining to Travis her understanding of his murdering Brandon and Derek in revenge for Chris.
- Priest (Caused, Alive)
- Thomas Abigail (Indirectly Caused)
- Twenty-seven members of the church congregation (Caused, Alive)
- Possibly numerous counts of unnamed people (Caused and Direct)
- Herself (Indirectly Caused)
- Madison Clark (Caused)
- Daniel Salazar (Either Before or After Reanimation)
Madison locks the gate behind Celia, leaving her to get devoured by walkers and then burned.
- The casting call for this character used the name Carmen.
- She was described as "Mexican. Carmen has lived half of her life in the United States. A strong presence with a generous spirit, Carmen exudes wisdom and grace. She is a woman who cares for others' children as her own".