So it goes back to the original question. Just because she claims to be treating a paitent it makes her not a prostitute but a woman at a high price escourt service or a street walker at a truck stop that does the same thing is? What would you think if your spouse was seeing a sexual surrogate with out your knowledge? Oh no honey I wasn't cheating she's a doctor. We were having sex but as therapy not pleasure. I didn't tell you because I was embarrassed. I can hear Tiger woods now. No wonder he got cracked with a golf club.
Why do you go back to the sleaze factor? Why always the worst possible idea? What if you were a single severely disabled person who was trying to have as a best a life as they could, who had a normal sex drive and this woman could provide you with the sex life that 'normal' people take for granted? Sure she takes a fee for it but even if she didn't people would still call her names.
We also don't know the conditions she puts on her therapy, she may be far more moral than you give her credit for.