Late response but I wanted to add that yes, prostitution is legal in parts of Nevada. Most notably Pahrump, NV. You can google this info. I was wrong about Las Vegas although they do have many "escort" services that are pretty honest with their wares. Prostitution isn't a federal crime, it's handled locally by each state and in the case of Nevada it is handled on a county basis. You can see that in the Texas law posted previously you would be prosecuted by the state, not federal government.
I'm honestly not being "open minded" or "forgiving" about this situation. I'm saying it's not the guy's decision. She's doing what she wants with her life and he can't change that. No value statements, there's just nothing he can do. Legal or not, good or bad, helpful or harmful, he's got to decide whether he wants to be a part of that or not. He's decided that he can live with it. Whether he likes it or not is actually rather irrelevant.
And as for the safety of the profession, there are many other professions out there that do have physical, mental and biological risks that are deemed okay by society. I don't think safety is the real issue. Would it be okay if she was a porn star? A stripper? Someone that pretended to have sex on stage (an actress--like Angelina Jolie)? Posted naked pictures online? Had phone/cyber sex for money? These are all non-illegal, safer avenues that, yes I would have a problem with. But if I take my partner's money and buy food with it/pay rent with it I've made my choice.
I apologize if that came out as a rant. I just wonder how much it really bothers him if he's still there and going on a "Jerry Springer/Jeremy Kyle" program to garner a little sympathy.
BTW, did they mention how they met? I'm rather curious if he was a customer.