congrats on almost being there! my nursing school interview with the dean of my school was a one on one experience. so, i can't really speak for the group interview type. but, i can say what i remember of my experience. it honestly didn't feel like an "official" interview it was more of like a chit-chat with a friendly person, experience. yes, i was nervous beforehand, who wouldn't be.
the dean basically went over my whole application portfolio (transcripts, entrance exam, essay, references and recommendations etc.) and asked me some personal questions as well as my reasons for attending the school and why, and other things. it was a formal situation, but it really felt relaxed and informal. she put me at ease right away. she pretty much wanted to get to know me on a one on one basis.
to put a face to my application, if you know what i mean. i enjoyed it. she's a very nice lady, great sense of humor and personality.
i can only imagine in a group interview situation, it would be somewhat the same maybe. except that you'd be with others at the same time during the process. maybe the interviewer not only wants to get to know you, but also wants to see how act and react with different people. or, maybe its a time issue with the interviewer who is wanting to do it all at once. i don't know.
good luck with your interview.