I agree that looking at some standard interview questions is helpful as is preparing a few questions about the school that she can ask about. Firm handshake is good advice as well. Most important thing is to be herself, let her interest in the school shine through and make sure they know that while she appreciates the scholarship she was already awarded, that having this scholarship will make a difference in her final decision.
One additional suggestion…when my D went to interviews, she brought a couple of copies of her resume in a folder with her. If your D has one prepared, I’d have her bring it and offer it to the person conducting the interview. My D felt that having the resume allowed for a better conversation as the interviewer could target questions to her interests/activities and she could talk about things she was very comfortable with.