Having worked for many years in the retail/wholesale industry.....she will find that the major buying programs (Macys, etc.) hire from all majors - liberal arts, business and fashion merchandising. These days, an aptitude for math is as important (in some cases more important) than a "good eye."
She should search the career sections of the websites for major retailers. There will be info. on the backgrounds required. Most entry level positions in merchandising are Planner or Assistant Buyer. Here's some info. from the Macy's site: Merchant Organization Macy's Jobs
And from the Belk site: Careers at Belk
Many retailers and wholesalers offer internships. Whatever major she selects, she should try to get a summer or term internship.
If she finds a school with a good business school and a fashion/merchandising program....she could major in a business discipline like Accounting or Marketing , and take courses in the fashion merchandising program.
SUNY Oneonta has a joint program with FIT in NYC, and University of Cincinnati has an excellent Design Program and you might be able to take courses in the business school (or visa-versa)
However, you will find that many people in top merchandising management at the larger retail operations did not have formal education in fashion management.