I think even though that was (probably, hopefully xD) meant as a joke, I disagree. Depends on whose viewpoint we're talking about. In this case, it would be imaginable, that Stacy
wasn't a secret spy from
our POV, if we could see her story independent of the MC's POV. So the MC and other characters wouldn't know, but we would, and would therefore not consider her being a spy a secret.
But in this case, she obviously
would be a secret spy since we don't know whether she is or isn't.
All that being said, I sincerely hope that not too many people consider my previous post to be taken seriously in any way