Suits You, Sarah

 is an unmarked quest in Fallout: New Vegas, given to the Courier by Sarah Weintraub.

Quick walkthrough

 * Talk to Sarah and bring her at least 30 jumpsuits.
 * After that you will be able to have sex with her, be well-rested and have a discounted stay.

Detailed walkthrough
After following the right dialogue tree, the player will be able to bring Vault jumpsuits to Sarah, which will result in caps, Strip reputation, and a discounted stay. But she will not accept them stolen from the guest rooms in Vault 21. With a barter check of 65, she will accept Boomer jumpsuits and Boomer flightsuits. She will also accept Vault 11 suits, which can be located at the dressers of Vault 11 Living Quarters. There should be at least 20 suits there. Vault 3 suits can also be bought at Mick and Ralphs but they will only have 1-4 suits during your first visit, once you've purchased them they do not restock Vault 3 suits afterwards. (for a list of vault jumpsuit locations see here).

After bringing her 30 Vault suits, upon revisiting her she'll mention missing the player character. You will then be able to have sex with her as you both "catch up" with one another, which gives the "well-rested" bonus (which is normally absent from the hotel room beds she offers). Also, after 2 speech checks, 50 and 75 respectively, she will agree to having sex after receiving suits, along with accepting Boomer suits.

You have to go to your room (which is the room left to Sarah's room) after work hours and she teleports to your room immediately. If you also put a sexy sleepwear in her inventory, she wears it for you. If you remove her vault 21 jumpsuit while she is still sleeping she will put on any other form of clothing you put in her inventory but won't remove it again.

Bugs

 * Sarah won't accept the Vault 21 jumpsuit you are given at the beginning of the game.
 * Sarah will sometimes use a deeper female voice upon greeting you or after finishing a trade.