There are plenty of people with MBA's and JD in the music/ent industry, especially at agencies. This is a non-traditional route for advance degree holders since the payday most of these students are seeking is much further out, but in the long run, being educated and having a solid degree will help to differentiate you from the HS graduates and the kids who called on daddy for a favor, especially when you both have equal experience and are hoping to move into senior roles, an education validates you, regardless of the common misconception that it doesn't matter. In UG, I was originally interested in this path, but I honestly couldn't deal with the low/no pay, it wasn't worth it to me.
After finishing her MBA, she can still expect to be in a low paying role with people who have fewer academic credentials, but in the long term, she should be able to advance more quickly. I'd tell her to really look into all options in ent/music, I would stay away from the record companies right now and look to work for publishers and not the individual magazine. She should also look at studios and film companies, they usually have more defined MBA career tracks.