I understand what confidential information means, but can a person be confidential? Can you use it to describe a person who you can trust with sensitive information? "She is organized, resourceful and confidential?"
A person who can keep a secret (confidential information) is said to be
The woman was his mistress and confidant.
The manager discreetly handled the situation to not draw any attention.
The concierge was tight-lipped about the personal matters of the hotel guests.
Her trusted aide never revealed what happened behind the scenes.
I can think of one sense in which a person can be "confidential". It means somebody whose identity is confidential. The term "confidential informant" or "confidential source" can refer to someone who gives information to someone else under an agreement not to publish his or her name.