> The actress is free to decline the offer.

I'm not so sure about that. That's entirely the point here.

I think the difference here is that there is a work contract, but the sex isn't mentioned anywhere. If you would write that in the contract, then you would be right it's "just" prostitution. But in the cases we are discussing, that's generally not the case.

The situation between employee and and employer is generally not that of two equal-powered persons, which is why we have tons of protections there, including doubt if sex was really consensual.