Now that is interesting, Timo ... I just went back to watch the sequence in question and there's no appearance of a secretary anywhere in that scene. There's a male officer at communications. A yeoman who comes to Pike's side with a form that Pike refuses, crewmen at navigation and helm, a male crewman at engineering, and a security officer next to the turbolift.
Spock moves to his console (which seems closer to the main viewer than it should be) and is looking directly at the slides from the side and doesn't appear to acknowledge any kind of assistant.
Do you have a source indicating the existence of this secretary? Or did you mean that the scene was shot with a production member off-camera, watching Nimoy's gestures, and changing the slides accordingly?