I have a degree in Marketing, though it really isn't related to what I am doing now for the company.
What I would suggest doing is to keep an eye out on the Disney careers website when they post internships and see what looks interesting. If there is a general trend of jobs, then see what they are looking for. What degree do they want, what experience do they want, things like that. It's important to remember that experience is more important than a degree. The reason I was able to get my job with a marketing degree is because of the experience I gained in another internship.
The college program is a great way to be introduced to the company and get frontline experience. CPs also have the opportunity to network with others inside the company to see how they got where they are, what they recommend, and just create important connections. From there, she should look into a PI. I would suggest trying for one following graduation so that she can complete a full year without having to extend school any longer, plus it opens the door for immediate transition into the company should an opportunity arise.
You mention that she is good at math. What is it about math that she is good at? There are many paths that math can take you throughout the company, but if she enjoys the process then maybe look into industrial engineering. It is a very popular degree within Disney and seems to give a pretty good base for a lot of businesses within the company. Otherwise studying something like statistics could be useful as well.
Going the route that you have suggested (finance) will not have her being one of the people walking around the parks - many of those are area managers and probably have a very different path than those that are working in an office. If she does the DCP, then she will get to understand those pathways as well.
(I'm going to say this again because it's not something I was told in high school while choosing my degree) Experience is key. She should look into summer internships, shadow professionals, anything that will expose her to different businesses and professions before she has to pick which she wants to focus on as an adult. On my team, I know that 3 of our degrees are Marking + non-profit operations, information systems, and HR, but now we all are basically data analysts. The reason we were able to get onto our team (through the professional internship program) was because of experience we had prior to applying.