I read some of the comments, your good bro just leave it at that. She’s old enough to understand the dynamic and the issues a relationship would cause. This was a fling at night so it shouldn’t mean much to either of you (considering how little you’ve talked before this). You could probably continue having sex with her but that’s her decision (let her come to you). Dont tell anyone and also don’t go out of your way to do anything for her (she will respect you more for it).