Every once in a blue moon something legitimately shady happens and it gets tossed aside along with a bunch of legitimate rubbish.
A secret is something known to two people, one of whom is dead.
In the absence of the truth, there will ever only be theories.
The GP's statement can be reworded as a kept secret implies at most one living person knows it. Leaked secrets aren't counter-examples to the GP's statement.
Assuming Charlene isn't a murderer or a ghost (i.e. all of her secrets involve one of the parties being dead), she reinforces the GP's implicit point that it's very difficult to keep a conspiracy a secret unless one of the conspirators ensures all of the other conspirators die off shortly after.
Honestly it's a coin toss