No I don't. I assume, being a trusting soul, that if she turns out to be a prossie thst she will ask the "going rate" or I will have to tell her to fuckoffnicely.
The rule is never ask how much until she mentions it. (Obviously, since she is to all intents and purposes a civvy.) The lovely thing about this is that she may indeed be just that - a civvy that is loitering for some fuckknowswhat reason. Not happened often, but as someone that used to enjoy a fondness for SWs I have actually been well surprised on one occasion. Hi, chat a bit, do you want a lift/fancy a drive, drive somewhere reasonably secluded but not scary, wait for price list plus blow job or eye contact plus blow job.
Of course the OP is thinking of some tv personality type or legal secretary walking down Highgate in her Jimmy Choos. And I think the answer, as with most just reasonably attractive women who start selling their fanny:
How much could she charge?
A lot less than she thinks. Her prize bargaining rag is to her worth some poor sucker's life earnings; whereas a savvy punter just makes a mental checklist of her assets and sees where she fits on his scale of reasonable affordability. What she fails to realise is that, now she's become a prossie, her fanny-worth has dramatically declined!