There's really no way to tell if the girl is having real orgasms or not. Even when a girl "squirts" in a porn scene she's usually just peeing.
There are some performers, like Jenna Haze, who give such enthusiastic performances that it's easy to believe that they're enjoying every second of the sex.
Well, unless you're relating a circumstance to yourself you can't be 100 pct. sure of anything you perceive involving another person.
But there are ways to reasonably discern whether a person is lying, happy, sad, etc....even whether a woman is actually cumming. Like I've said before, there is a reason doctors can tell whether your response during reflex tests are a result of reflex or a result of deliberation...further the contrived deliberate behavior of most people trying to seem like they are enjoying the sex but really thinking more about the check than the sex.
Most orgasms (for example) cause the person to respond reflexively not deliberately. If you encounter them enough and it's something that interests you then you should be able to at some point discern the reflexive behavior of most real orgasms from the contrived, deliberate behavior of most fake ones.
To that end and per se orgasms aside, some of the girls I've seen who appear most into their performances are; Brea Bennett, Vega Vixen, Samantha Ryan, Marlie Moore, Avy Scott, Keri Windsor, Rebeca Linares, Jewel DeNyle, Lela Star, Aletta Ocean, Blue Angel.......
