Miriam,
I agree. Dismissals should be done privately, behind closed doors. I have also learned over time to have another person in the room, usually from Human Resources. I would try to have a man from HR in there with me so that gender does not become an issue or accusation. As you say, you want that person to leave with dignity and respect so delivering the message accordingly is important. Be factual in delivering the message. It is never easy to dismiss someone but can and should be done professionally.
Pat
