I don't really have a good answer for you. Respectfully though, the idea that she's become some kind of high class prostitute just doesn't add up. But believe what you like, there doesn't seem to be a good way to prove it or not.
Story time. I tried to hire her for a private "date" many years ago, I communicated with her management more than once. Basically she was available for interviews, business meetings, these sorts of things... but it was made clear, absolutely nothing sexual was going to take place. And just getting a meeting was a very expensive fee. It wasn't worth it for me at the time.
Her management was always very protective of her. Not like in the west where an agency would have been whoring her out to every porn studio, photographer, expo, etc... that they could manage. Rather, her Japanese management seemed to have a lot of respect for her. Though I often wonder if that was her wish, or if they were just being greedy and unwilling to turn their prized client into a cheap whore, kinda like the way an athlete doesn't sign 500 autographs every day, as it devalues the commodity. I know that HItomi had specific desires to do more works and that her management forbid certain things.