There seems to be a big difference in the styles of porn performers, some want it to be strictly professional and others want to push for a semi-romantic style of interaction.
I imagine performers with partners are significantly more likely to be the former, while their partners are clearly okay with them fucking other people for work they likely draw a line somewhere and usually that's things continuing outside of the actual scene.
It's like dating a stripper, you might be totally cool with her getting naked on stage, but if a dude kept trying to convince her to give him private shows at his house you'd probably have an issue with it.
I think the only relationships that don't cause complications with porn scenes that involve some additional fucking/making out would be polyamorous ones.
