Sweetie started out as a prostitute on the Strip, working for the Omertas in Gomorrah. Although she wisened up to the free chems they gave out to prostitutes, then began to charge, she decided to work for Pretty Sarah instead.
Her name is Sweetie because, in her words, she is "the sweetest piece you'll ever find outside the Strip." Unlike her male counterpart, she will sleep with either males or females, if the price is right.
A Bit of Slap and Tickle: For 300 caps, she can be hired as a prostitute by a Courier of either gender, not being particular about her customers, as Maude puts it. This strangely takes no in-game time.