I attended both last year and there isn’t a huge difference. The main thing she’ll miss is that after the tour there’s a panel with professors and a panel with students. Also in the big room where the panels are there are a bunch of booths set up (kind of like a job fair) for things like greek life, study abroad, etc. I think the black and gold days are definitely worth it, but the tours and info sessions were full of information so she shouldn’t miss out on too much!
I would also recommend that your student do a Dore for a Day visit as well as go on a tour. The Dore for a Day experience really allows a student to see what it would be like to be a Vanderbilt student, as well as giving them an opportunity to sit in on a class.