Really interested in seeing a provider, but no reviews anywhere. Her site looks legit and her calendar shows travel to various cities. But...she states on her site that she asks clients to refrain from writing reviews for the sake of privacy. Is that a red flag, or am I being paranoid?

For personal or privacy reasons, I know a few however, I feel that as a newbie, you should refrain from those and start with well reviewed providers here on TER so you don't encounter surprises. Reviews are a significant way to know that you are meeting the "real deal" "Taking one for the team" should be reserved for more experienced gentlemen and even they would prefer to get a recommendation from someone else who has seen the lady

You are not being paranoid.  Even as long as I have been doing this, I still avoid providers with no reviews, unless a trusted hobby buddy or provider I know well vouched for her.  Better to be safe than sorry.  There are many providers that do not want reviews, for reasons of their own.  I agree with Paloma's advice, stick to well-reviewed providers for a while.

but this is  REVIEW site. If a provider wants to use TER to generate more business and has a "no review" policy, she should be banned.

This is a review site, and I agree that if a provider wants to use TER to generate business, she should allow reviews here, or not be allowed here.  She can always tell the guy not to be too explicit in his narrative of their date.  My early reviews were kind of explicit, but as I got more experienced, I toned them down some in terms of language.  The story still got told and there was no doubt as to what happened.

It appears that *she* made the *choice* to not not be affiliated with TER.  
She does have that option.
Many providers asked to be "delisted" from TER. This means no reviews can on will be posted.  
Yeah...I know, I'm on her and post chit but to say she has zero say in the matter is freedom. Everyone is free to do as they please within reason.

Damn, that's what I thought. And she appears h-o-t. Would it be unprecedented for me to ask her for a reference?

Why not? She may not want to use TER, but I do to make sure I am seeing a legit provider.  

I'm not going unless I get a reference from people I do know.   Have you Googled her stage name,  phone & pictures.  Tineye picts too.  She must advertise somewhere...   I'd search all the ad sites for her name & phone.
Frankly this is too much work.  I'm going with someone whose reviews are not hard to find.