There was a local provider I was checking out and she had about 6 good reviews on TER.  Suddenly her reviews and profile are deleted from TER and her website is down. Obviously not a good sign.  But what normally is/are the reasons for this?

and no one can know without more information.  If she had a rules violation on TER, then I'd expect her web site & advertizing to still be up.  There are a whole list of possiblities

She has her reasons which we may never know, but it sounds like she's still in control of the administrator data so that's a good sign she's okay

There could be a number of reasons why.  From my own experience, she could simply have decided that she no longer is available and deleted any trace of her time as a provider.

To me, the most likely reason is that she has decided to exit the hobby as her own decision.  Since her website is down, she apparently planned her disappearance, and was not forced out of TER by admin.  The reason could be anything.