I'm risk averse by nature, yet I've been near the first reviewer before.  If conditons work, I'll jump.  There are a couple guys that I trust implicitly, so one or two would work.

For most newbies, it's a bad idea.  Still, you have to decide how safe is safe enough

I have rolled the dice a few times and it worked out well. With only one or two reviews it would depend on how old they are.  If she has only been in the biz for a short time she is not likely to have a lot of reviews. The key is, as you said, the reviewing history of the guys who wrote them.

risk.  6-8 reviews gives a pretty good cross section...  if a few are experienced reviewers...  
1-2 is too few for my tastes.  I don't cross off the list but pass for the moment & circle back later.
skb

Here's your answer in the form of a question:

(Click link.)

touring your area, it is your call.  No such thing as risk free.

I put more weight in the reviews of a guy who evaluates providers the way I do.  The women he gives high marks to are the ones I give high marks to, etc.  If it is a couple like that who speak well of her I'd feel comfortable.  Otherwise I'd want more of a sample.