Sierra was born in 2251. In 2277, she is a fair-haired twenty-six year old woman who shows little regard for matters outside consuming and hoarding Nuka-Cola and collecting merchandise relating to it, much to the dismay of her neighbor Ronald Laren, who remains in Girdershade in the hope of seducing her. Her fanaticism for the drink is without question, as she subsists solely on it. She has spent every bottle cap her parents left her acquiring the drink from merchants, travelers, and towns spread throughout the Capital Wasteland.
The Nuka-Cola Challenge: Sierra has her own Nuka-Cola "museum" (a display of her collection within her shack) which she gives tours in. After completing the tour she will give the Lone Wanderer an ice cold Nuka-Cola and asks them to gather 30 Nuka-Cola Quantums for 40 bottle caps per bottle which adds up to 1200 caps. Completing the quest her way grants good Karma.
She is the only non-player character known to be addicted to Nuka-Cola Quantum.
When asked about what kind of recipes she can make with Nuka-Cola Quantum, she says it's so rare, she only knows one. However, when she sends the Lone Wanderer off to get the 30 Quantums, she may say, "Hurry back, maybe I'll make some of my legendary Quantum Sorbet!" implying she knows more than one recipe.
She can reveal the location of Evergreen Mills through dialogue if asked if there is anything else interesting in the area (she warns the Lone Wanderer to stay away from it).
If told about Ronald Laren's sexual intentions for her, she will play it off as a joke on her.
In Fallout Shelter, it is possible to find an NPC with a randomly generated appearance bearing Sierra's name in random encounters in the wasteland.
In the Fallout 4 add-on Nuka-World, fulfilling John-Caleb Bradberton's request of letting him die at the end of the Cappy in a Haystack quest, after accepting Sierra's request to not kill him, will result in Sierra insulting the Sole Survivor before turning hostile, not only due to killing her idol, but also for lying to her, just to get her prized possession, the Nuka-World jumpsuit. Players intent on securing both the powerful Nuka-nuke launcher and her much less useful Nuka-World jumpsuit can either kill her, leave the area quickly after she becomes hostile, or use console commands to no-clip through the door.
In Nuka-World, Sierra's teeth appear to be rotten.
pcps3xbox360 If you kill Sierra and then steal items from her house, she may protest, even though she is dead. [verified]
pcps3xbox360 If you fight any creatures outside of Sierra's house and then enter Sierra's house, you will not be able to communicate with her because she is fleeing. If you enter her house while enemies are still nearby, she will flee the house and disappear forever. Sometimes, she may run for cover at another house in Girdershade and can be found there, rather than fleeing town. [verified]
ps3 If you plant an explosive on Sierra and then ask her to make a Mississippi Quantum pie, she will start making it, but explode during the process. The player is stuck waiting for it to be made. Loading a previous save fixes this problem. [verified]