I just returned from an interview there not over 3 hours ago and the best thing that I can tell you is to just relax! I know that is easier said than done but this interview will be the most laid back one you will ever have. I was the very last person to be interviewed out of 20 so I had the opportunity to quiz each person as they returned. The overwhelming reponse is that the interview was purely conversational. It is a chance for them to get to know you as person. I was asked "Tell me about yourself", "What kind of practice do you picture yourself having", etc. The most challenging question I received was "Tell us about an ethical situation that you observed during your employement at XYZ hospital".
Seriously, don't freak over this one! From what I understand, if you have recieved an interview, then they are interested in you. It is just a chance for you to view the school and see if it is a good fit for you. I was told directly by someone there that UHS simply doesn't want to waste the time interviewing a thousand people from which the vast majority would not be accepted. Acceptance rate for inteviewees is close to 90%, so you're almost in! Good Luck to both of you and let us know how it goes!
P.S. I was very impressed with the school and would attend if accepted.