The producers are very selective in what they show. I assume the rest of the campers probably guessed there was something wrong, as they were away from the camp so long.
There was no mention of Phina being given treatment as well, from Lauren or Phina herself. This was probably edited. The producers know that the average viewer is very easily manipulated, (one dimensional thinking) so they don't even have to try too hard!
I assume that they all say negative things about each other sometimes, it's only natural considering the situation they're in, we just don't see it all.