Yes, this is unfortunately true, as I'm the administrator of an organization's Facebook page, and I've deleted some spam posts or a couple really random ones that people posted to the page. If there are any sites for Belgium that have doctor or therapist reviews, you should be able to post one on there and have it not taken down.

Actually, looks like you can't delete reviews (I just went in and didn't see an option), just posts to the page. So you might be OK. But she also might be able to complain to FB about it and have them remove it. Worth a shot though.