Galaxy
Sorry Dickens I wasnt having a go at you, I just nicked your phrase to express my position 
Apparently the phrase was first mentioned in 1622 by one Gerard de Malynes - in a book about trade-law and quoted the Dutch proverb "leuen ende laeten leuven". (Yeah, I just looked it up!)
But, in the context we're talking about it's usually directed at those who are critical of another's life style / choices. The added ryder - 'as long as they are not harming anyone' is the rub though.
In the wider context, being freely available to be purchased for sex (which I assume this woman is) through choice may not harm her - nor directly her male buyers... but what's the subliminal message being given to men? And, what about the wives and partners of her clients, they certainly are not all single.
As Indigo8 says above, There is an established link between men who use prostitutes and men who violate women.
I'm not a prude. If people freely want to engage in sex with each other because that's their equal choice in the matter, it doesn't make me clutch my pearls, but buying a woman's (or vulnerable male's) body, sinks my spirits. And this woman is - for all her jollity and joie de vivre - just perpetuating the woman-for-sale trading.