Olive serves drinks and "entertains" patrons of Sam's shady back-alley bar. It's the best-paying of all her jobs... but the rough, decadent work screws up her moral views, makes her lose faith, and affects her emotional stability.
Stay far away from this job, unless you REALLY know what you're doing. It severely cuts through your Morality and Faith, which not only puts you in risk of bad endings (though some players do aim for these in particular) but also raises her chances of being delinquent. The Charisma raise is simply not worth the stat losses you'll take, and you shouldn't be needing the money from here. At best it can only be recommended in small doses, if you want a quick Charisma/money raise for something and aren't at age 16 yet. Once Olive reaches that age, the far better Cabaret work will be avaliable.