Outside of the quests, there are three general events. Flashing certain characters will cause them to grope her (some rub her ass, some finger her, some rub her tits).
For the last, once you purchase the ability to give blowjobs (the third 3000 option), you can get the dark-skinned hobo-looking guys to follow you around (talk to one while clothed and choose the first option; she'll flash him and he'll start following you around). You can change the A key's binding so he flashes her, or you can choose the last option, which means when you hit the A key she'll have sex with him (you have to purchase each option before you can use it - blowjob, titjob, and doggystyle fucking). This is also the fastest way to get money - each time you have the hobo stop following you, he gives you money, so you can just keep switching him between following and not following to build up money quickly.
