You really need to look at each site and see the context. If she's actually an international Playboy model that pulls in £10k for a Photoshoot with a famous men's magazine then it's unlikely she'll be pretending to be a Romanian escort in a grotty bedsit in an English provincial town offering anal for £50.
However as others have said if it's a series of escort websites, even foreign ones, then she could well be genuine. For example some glossy pics turned up on an agency website in Newcastle, reverse image search showed an escort agency in Brussels with the same pics of a Latvian girl. A member saw her and confirmed its the same girl (although the pics were photoshopped) just doing the rounds.