This can be a touchy subject, so let me see if I can be diplomatic...
First, I definitely think that there are enough ladies who make an honest effort that if you run across one that doesn't, you should leave. I don't think anyone should ever just suck it up and knowingly waste their money from the door. There is a YMMV aspect that you should expect when you do this, but flat misrepresentation is unfair to both the client and the quality providers out there.
That being said, me personally, I would at least throw $100 down. That's not because I think she should be rewarded or compensated in any way, it's just a good faith move to try and smooth out any possible repercussions. I know some will disagree with that approach, and I'm not saying it's right or wrong, just that I would leave a flat walk out to someone braver than me.
It's never happened to me, but I do know some ladies who have experienced a walk out within the first 10 minutes. One girl really was very sweet, a total southern-girl-next-door cutie, but a little too GND and not enough PSE/model material for the guy, and it really hurt her feelings, even though he was apparently very nice about it. Another was using 15 year old pictures, had walk outs happen regularly, and didn't care at all. Me? I would only review in the second case. Personal taste is one thing, deception is another, and if she's at least trying, I would like to give her the same treatment. Partially because of who I am and seeing how hard a friend has taken it, and again partially to avoid any drama that may unfold.
I am, of course, not referencing any obvious walk out situations here, like you booked with a 20 year old blonde spinner and a 60 year old Slovenian cook shows up. Just trying to help with some of the grey areas I've seen show up over the years.