Why lie to her? I don't get it.
If she misrepresented herself just say that.
If she didn't and still she's not your type then give her $20 for her time. Try to ascertain if she is your type before you go there.
Please remember that there are prank callers who go so far as to set up an appointment and show up only to say they changed their mind. Really they just wanted to meet us for free so they could go wack off to the experience.
I have only had that happen once in the last year where the guy said I wasn't his type, and I was miffed, especially since I turned down a regular for the guy. I asked did I give you a description? Yes. Was my description accurate? Yes. "There is usually a charge, you can't just go around meeting girls for free, I will let you off this time since you didn't know" I said. He ran even though I was polite, I just wanted to discourage this type of behavior.
It's like making an appointment for a haircut, you can't show up and say "oh sorry i wanted a younger woman." This is our business, our livelihood, please don't mess with it, and please don't play us for fools and lie to us! Thank you.