I am sure she already has several good or great reviews or you most likely would not have booked with her in the first place.

If you score her on "what might have been" you aren't really being honest, or adding anything of value to the review database as "what might have been" never happened.

I think you should go by your first instinct and simply skip writing a review at all.

BTW, do you plan on trying it with her again? If so, you could simply wait until after the next session to write your review.

there is no upside to writing a review under these circumstances.....

because no matter how you try to give her credit some others may wonder if there was something about her that put you off or wonder if they would not do well with her either - it just does not reflect well on her from a business standpoint, even though you and I both know that  sometimes you are just not as up for it as you want to be, or sometimes it's really just a lack of chemistry that is neither party's fault.  Best to leave it lay, so to speak......

I've had my share of such disappointments and have nevertheless posted reviews about them —including two with two of the most adorable ladies I've ever met anywhere, under any circumstances.

Note that the number rating system, for all its flaws, does have guidelines that, if followed, make it possible to review a provider fairly under the circumstances.

First, a provider's appearance is not at all dependent on one's own performance.

Second, note that the guidelines for assigning a numerical value to a provider's performance are fairly specific and, again, don't necessarily depend on one's own performance.

Third, the "Juicy Details" section allows for plenty of commentary on the session.  The OP's posting outlines what his review could state in that section.  All that he would need to do to comply with the rules for the that portion of a review would be to add some description of specific acts.

And presumably there were some acts.  "She did everything right," he writes.

Recall the old National Enquirer catchphrase: "Enquiring minds want to know."  Take it from there.

Finally, when I read a review, I'm interested in learning about the provider and the experience of her in as many ways as possible in order to help decide if I want to see her.  This doesn't require a heroic, Henry Milleresque essay boasting of some other guy's own feats in the bedroom.  I want to be able to insert myself, so to speak, in the picture

why make your negative experience hers?

What's the point. You pay for VIP, correct ?

I don't review every provider I see.  In addition, if a down experience is not her fault at all (i.e. body is not my type, we don't click at all even though she tries), I don't let my bad turn into her bad.  On the other hand, if her 'faults' are something she has control over, and many others would be put off  then  think about letting her know at the end of the session or writing the review

Because there is no other reason to write THAT review. I write reviews to benefit the lady and/or to inform fellow hobbyists of good or bad experiences. Yours does neither.  
Pay for your VIP or write some problem reports. (or find another girl to review, or see this one again)

... and the minimal douchery.  Borderline minimal.

I decided not to write the review.  If I did, it would have been a 10/8.  !0 for appearance because she could have been a model.  8 for performance because of what it could have been.  The review wouldn't have dropped her score but yeah, it would have raised more questions and would not add true value to the reviews.  I'm already paying for VIP so I'm not doing it for free days.  Honestly I would've wrote the review strictly for her benefit because, like I said, she did everything right and was a sweetheart about it.  No other ulterior motive.   She is someone I would try again if she'd have me back, and if so, the next review would be more value because I know I'd be back on my game..