How do I remove or delete a review?

...the bottom of the page. Give them your reasons and see what they say. Once you have submitted a review it's their's. I don't mean to say they won't remove it but it has to be for a reason they deem legitimate.

which is up to TER Administration's discretion to allow.

It means you may have to have another session with the provider if the last one is over 3 months ago.

Did the provider ask that the review be removed?  If so, then she ought to be the one to contact TER Administration about it and say why, though it doesn't hurt if you also chime in in support of same.