Hey Shyguy,
First, let me say that I, for one as a noob, have appreciated and benefited from your honest, insightful, detailed reviews. We have seen a couple of the same providers and there are a few more you have reviewed on my favorites list.
I think I'm in a similar situation right now. I saw a provider nearly two weeks ago and still have not submitted a review. By far the longest I have gone without getting it in. To be honest, we just didn't connect, as you sort of said here. I think she's sweet and tries hard but we just didn't have the chemistry and I haven't decided what exactly to say. I wrote up a review that details all the reasons I think we didn't really connect but I think it's rambling and nobody would read it all. Also, I don't want to hurt her feelings or her business. On the other hand, I wrote glowing reviews of the first few providers I saw, when I was new to the hobby, when I thought this just is what you get in P4P, that I wish I could have back. Not because they are "bad" providers and now I don't like them, but because it isn't fair to the better providers I've seen since them and can't rate any higher, even though they deserve it.
You acknowledge that a provider, like anyone else, can have a bad day. You acknowledge that nobody has perfect chemistry with everyone. I have the feeling you realize that imperfect chemistry COULD be her problem as much as yours. I think all that adds up to this: you empathize with the providers and if you write a review that you feel is honest, it will also be fair in the grand scheme.
This place was started to help and benefit the hobbyists, not necessarily the providers. I have had the same dilemma: "I don't want her to read this and get her feelings hurt". But, if you aren't honest, you aren't being fair to the other hobbyists or the good providers!
If you think she tries and is safe and sweet, but you just didn't connect then say so. If you don't think she much cared, then say that. Either way, I think the hobbyists and the providers who really try to bring it will appreciate it.
Also, I don't know who you had this not so great experience with, but one not great or even negative review won't make or break her. I've got a provider who's been in my favorites for some time. I like her ad and her website, and she has a few but not a whole lot of good reviews so I've known I want to see her but because she's WAY across town and somewhat limited availability, it hasn't happened yet. The other day a new review popped up for her and it isn't good. It gave me cause for pause, but I thought what's one guy. Maybe she didn't like him. Every provider I've seen has told me I'm very sweet and asked me to come back so I probably won't have a problem with her. Still, the negative review bugged me a bit. Then she got yet another great review and I know I'll see her eventually. My point is that one negative review won't end her, and if it will, she probably needs to find a new career anyway.
Also, you're obviously a fair and conscientious guy, as conscientious hobbyists, we will take your review and her others and whatever other research we turned up and make a decision. We will appreciate your honesty and, I suspect, so will the quality providers. The fact you are worried about hurt feelings/fairness says a lot about yourself and your reviews. I just think honesty is the best policy here. I don't think that coming from you that honesty will give an inappropriately dim view of the provider.
Good luck in deciding what to say! Like I said, I'm in a similar boat. Hopefully this helped. Also, don't quit!! We all sometimes need a break from what we are doing, and that is natural. But don't let one negative experience push you out completely, please. A short break for perspective is one thing, but don't quit.
So yeah, others have felt this way. Feel the love. Go see your tried and true, favorite ladies for a while before you try anybody new and you will feel better.