Would be hard to say.  I would suggest doing some searching to find out if she is new, or has been around for a bit.

You should also look at the date.  If the review is from some time ago, you might wonder what's been going on since.  If it's recent, she might just be new.  Also, keep in mind; we're each only allowed to review a provider once, and many clients don't write reviews.  You may want to go to the provider's regional board and post a request for information.  That way, you may hear from those who've seen her but not written reviews.  You might also check on other boards, although I believe TER is among the best.

reviewed her has.  If he does not have many or none with providers where you can find reviews from other hobbyists, then you probaly should stay away.

There can be quite a few reasons as to why an escort might not have so many reviews, and not all of them are bad.  Some may have quit for a while, then came back into the business.  I figure the reviews are removed after the escort has not been active for awhile.  I had some excellent reviews on the doggie - something site, before I took a break.  Another reason, they changed their name.  I changed mine, not because of bad business or reviews, because a customer managed to track down my mom and ask for me by name.  I decided on using the hawaiian version of my name, just as a precaution.  And, like someone else said, not all customers post reviews.  Finally, the reviews may just not be on this board.  I advertise on a adult personals site, so my reviews are over there.

Ask the escort where to look for her reviews, or ask her customers about her.

Hmm, and maybe I'll have some of my customers post a review over here.  

Seeing any provider with less than three reviews can be "iffy", in my experience.  Putting much stock into a review done by a reviewer with only one review to his credit can also be "iffy".  Seeing a provider with only one review by a guy who himself has  only one review to his credit is asking for disappointment.  Particularly for a newbie.

For example, New York is rife with Asian ladies with one review from a single reviewer.  Generally, they wind up being AMP girls and the review was posted by their agency.  

This isn't to say that seeing a lady with only one review by a one-shot reviewer is certain disappointment.  I've found some real gems this way, and I keep them to myself.  But as a rule of thumb newbies should stick to the tried-and-true and get their feet wet.