I understand your concern. It is very stressing to think about what to wear to an interview.
At any interview, including school interviews, you have to wear business causal, minimal makeup and no strong perfume (body spray after a shower will be sufficient to make you feel fresh) No chewing gum (use a mint instead) and no sandals or open shoes (even if your toes look gorgeous!) No fake nails. Do not over do your hair, wear it very simple and neat, and minimal jewelry. I know... that does not have anything to do with you being the right candidate for their nursing program, but they really pay attention on details.
The rule of thumb is wearing dark pants, light shirt (not a t-shirt) and dress shoes. You won't get it wrong!! Good luck.