Sarah grew up in Vault 21. Like her brother, she suffers from agoraphobia and, as such, rarely leaves the Vault. After Mr. House took control of the Vault and made known his plans to evict the residents and seal it with concrete, Sarah and her brother convinced him to spare the upper level. By Mr. House's acceptance, Sarah won the ability to remain in her home, now converted into a hotel and gift shop with her as the proprietor. Sarah's brother was allowed to stay nearby, now working out of a warehouse immediately next door to the Vault 21 Hotel. Sarah and her brother seem to keep in touch via e-mail despite their physical proximity, likely due to the extreme discomfort both would experience from being outside even for the short trip between structures.
As vault suits are extremely popular items for the gift shop, Sarah is always on the lookout for extra stock. The player character can help her with this through the unmarked quest Suits You, Sarah. She can also be affected by the "Lady Killer" perk. Before accepting the "Suits you, Sarah" quest if your speech skill is high enough you can convince her to have sex with you as a part of the deal. (Speech skill level 65 then level 75)
With a barter check of 65, she will accept Boomer jumpsuits along with Vault jumpsuits. They will not count towards the 30 jumpsuits you need to give her.
If you kill Mr. House, you can mention it to Sarah. She'll be delighted that she now technically owns the Vault, but it otherwise has no effect on her unmarked quest.
Through certain dialogue options and after giving her the 30 jumpsuits, she can be propositioned for sex, at which point she will tell the player she will meet the player in their room. Sarah will have sex with the player regardless of their gender.
Suits You, Sarah: Sell her 1 vault jumpsuits at a time, you will gain vegas fame and 30 caps each. Eventually, her greeting will change to "if it isn't the Vault Explorer" to finally "Hey I've missed you". After about 8 jumpsuits or so, you will get option to meet Sarah and rest together. If you have companions, you must make them wait outside before proceeding to the first room on left in the vault. As you enter the room, Sarah will appear.
Tourist Traipse: Ask Sarah for the tour of Vault 21 and she will happily oblige.
If you insult her in any way she will become angry and say she "Doesn't have to take that shit from anyone."
Sarah has a picture of James and Catherine on the wall next to her bedside dresser, although their likeness is likely recycled for that photograph like other Fallout 3 assets were.
If she is killed, she will be replaced by a Securitron. The Securitron, however, won't buy vault suits.
Sarah refuses to rent you a room if you have negative Strip reputation. Strangely, she also refuses if your reputation is at Wild Child. Because of this, it's possible to lock yourself out of renting by raising your positive Strip reputation (going from Soft-Hearted Devil to Wild Child).
After having sex with her, she will stay asleep in your bed with her Vault 21 jumpsuit unequipped and will only reequip it after she wakes up. This means, if you pick her pocket, you can take the Vault 21 jumpsuit and she will remain in her underwear indefinitely. This leaves the option to dress her however you please, for she will equip any clothing item in her inventory.
Sarah is essential to Classic Inspiration; her death will make it impossible for the player to complete that quest, due to her brother becoming despondent at her demise.
pcps3 If you take her tour with companions, they may disappear and not reappear when you exit the Vault. Reload a previous save. [verified]
pcps3xbox360 After having sex with her and waking her up, she will have a different voice than normal. This also occurs when she greets the player in passing (without engaging in dialogue). This glitch may also occur at the end of a transaction. [verified]
pcps3xbox360 It is possible for her to not recognize that you have Vault 21 or Vault 19 suits in your inventory to give to her. The same problem can occur with any type of Vault suit if you are withdrawing them one at a time from a companion's inventory, but these issues can be fixed by exiting and re-entering the gift shop. [verified]
pcxbox360 If you pick the dialogue option to initiate sex with her without first getting the key to the hotel room, you will no longer be able to interact with her beyond a pre-programmed response; this includes getting the key to the hotel room. [verified]
pcxbox360 If you play a character with speech abilities high enough to use all the dialogue options (and you do it when you meet her for the first time), you possibly won't be able to have sex with her whether you have delivered any quantity of suits or not. She may sound as if she's going to meet you in the room right away, but she will actually stay in the shop. [verified]
xbox360 If your skill levels are below what is necessary to pass the two speech checks to initiate sex with Sarah (65 and 75), using chems (alcohol or Mentats) or skill books (Meeting People) may cause the dialogue options to disappear. [verified]
pcps3 Sometimes, when she comes to your room to have sex, she spawns with no hair. [verified]
pc Opening Sarah's inventory by getting into Steal mode reveals her having beer, bubblegum and crunchy mutfruit among other things. However, it can't be stolen (or taken from her corpse). The GECK classifies it as cut content as all items have a 0 count. [verified]
pc Changing Sarah's clothes (after stealing her Vault suit) will cause her to wear the last clothing permanently, as the clothing will disappear from her inventory. [verified]