I'm pretty sure Misa works for a hostess bar. These types of bars doesn't get sexual at all, it's just men paying to be served drinks with pretty women next to them. Moreover, the bar that Misa attends is a lesbian bar, there is nothing slutty about that.
And lastly, you shouldn't slut-shame. Sluts aren't a thing, and they'll never be. Both Misa and Ai are single, they can sleep around all they want. It's also important to know that the ladies that Misa sleeps with are well aware that she has multiple friends with benefits. And they all still chose to engage in sex with her. Meaning that she literally hurts no one's feelings during the process, nor does she confuse anyone as it seems that she makes these things pretty clear to her FWB.
Case close, no one is a slut in this series. If you can't get maidens just say so.
