The confidentiality is the main quality of a good executive or administrative secretary. Without this trust between the boss and the employee the confidence is not there anymore. During her years of experience working as a secretary the employee will develop and learn to keep things confidential.
The perfect one because there is, will be able to work and do her job without breaking this point of confidentiality. Believe me there is so many ways you can do that. By talking outside the job about the job it or what is happening. Talking about your boss or his decision or where he goes and its purpose of the trip. Hearing a conversation about something confidential and making your own comments. I can go on and on with the subject but that is not the point. If you cannot hold yourself from gossiping or being too curious being a secretary is not your place at all.
I have been a executive secretary in my young years and believe me I heard many things and saw things that I would never be able to reveal here. I was to be trusty by my boss and because of that I have receive great recognition in my work.
Keep that in mind if you are not able to keep things confidential, change job it is not for you.