I knew the twist going in, I just didn't realize how the twist was presented.
It actually does seem to me that the twist was built up and earned. There are several instances where they ask Angela about why she doesn't shower with the other girls.
She doesn't want to swim, shies away from physical contact. The romantic plotline with the boy at camp has several awkward moments including the first time he kisses her.
There were lots of good subtle clues sprinkled throughout.
Other than the twist though this was a good effort at the "kids die one by one at camp" formula.
It was an upper tier B movie and even has some good characters.