Lorraine was likely already partbof the Secret World during the events of the Park.
Think about it. She reacts to dull surprise when the park becomes spontaneously abandoned in a matter of seconds. And her flat mood while talking to a Nightmare Fuel inducing Bogeyman! Why is she not screaming in terror to any of these? Because she already knew the park was abandoned, and she and the Bogeyman had met before. And the only way she could've known all this is if she was already part of the Council. This is partly supported by the fact that the Bees tried to warn her in-game to stay away from the park.
Combination of depression and the case of Unreliable Narrator: we don't know, how much of all this actually happened and was not part of her delusions (and Mind Rape), while being depressed makes many surprises somewhat dull.