I don't doubt I posted something about ethics, but I'm not sure what you are talking about.
To answer you question, it depends on what the nature of the "ripoff".
If she just gave a guy lousy service, but she continues to give me great service - I'd probably chalk it up to YMMV. And I'd probably almost feel better about spending time with her. I'd never post a positive review of her - without heavy caveats about YMMV - because I don't want someone else to be disappointed.
If her service is lousy - and I expect and am okay with the lousy service she gives for some reason (she looks like a girl I wanted to bang when I was in HS). I would post an honest and clear review of her and why I was willing to put up with the lousy service in this case.
If she was accused of cash-n-dash, and it is something which you could imagine her doing (but which she's never done to you), I'd be more likely to hold off judgement - but also be wary of seeing her again.
If she actually did a cash-n-dash, or some other scam - and admitted to it. I would definitely hold it against her.
In all cases, character counts. To me, I owe the rest of the community honesty and respect - because I expect this from people. I hate it when guys post reviews which are in any way dishonest or unclear. The whole point of posting reviews is to help other people - not yourself.
I also can't stand guys who have just a few reviews, but post on this board all the god damn time. You clearly have something to say, you clearly use this site for information, you clearly can type. So share. Give back, or pay it forward.
If you think paying the people who make this site is in any way equivalent to posting reviews, you're an asshole and a leach.