With Bright Futures any money you don't spend is yours. I go to UF, and Bright Futures covers all of my credit costs plus a $300 a semester for books. I buy my books online or international edition and usually that costs less than the stipend. I still get a check though, and I use that money for other things. The basic rule for any scholarship/financial aid is that it can be used for anything as long as you meet the requirements and there are no exceptions for what it has to be paid for. That's why I never apply for tuition-only scholarships since Bright Futures covers that already.
So keep the money, and use it for other expenses.