1) She asked to be delisted or  
2) The reviews were found to be fake so removed.

 
I could also be that the review DB had some problem and those reviews were trashed, or some other technical "glich" caused them to disappear but that is much, much, much less likely.

Reviews Removed

I repeat with my faves.  I've had repeat reviews of a few removed.

YEMV

TER's rules, and the mods didn't catch it initially, then they can remove the review even after it went up.    There are specific service  requirements for a provider to get more than 7 points for service.  If a review is non-conforming, the mods will automatically disallow the review.  They do not allow editing of the narrative to conform to the score they WANTED to give, as this leads to fakery and then the review is worthless to other members.  

I've had a few reviews of my own disappear and then noticed those specific reviewers can no longer be found.    
These were real reviews which had been there for some time, then poof!  Gone.  
The reviewer and all his reviews had disappeared.  

is that the provider or someone else had strong evidence that the reviews were fake and had them removed.  

I would not consider this, on its own, to be a red flag with respect to my decision whether or not to see a provider.