If the profile is a professional profile that's used for her self promotion and she doesn't know you personally or interact with you in a meaningful way then book her, pay her, fuck her and post the review.
If she's a real world friend then have a wank over her pictures and videos then leave it at that. I've known a couple of women personally that turned out to be escorts and I'd happily shag them but the reality would be a lot more awkward than the fantasy.
If you do fuck the Facebook friend pornstar then it's probably best if you're a single bloke. Even then, if you do get a girlfriend in the future you may have to hope that she doesn't have a look through your old posts and spots any dodgy exchanges between you and the prostitute.