Oh Boy, Ft. Walton Beach has a Joann's. Pensacola has a super shop, A&E Pharmacy, Panama City has Quilting by the Bay quilt shop. As far as any fabrics in Destin proper, I really do not think there is much at all. Some of the places that have fabric on their signs are for decorating fabrics. I may not be 100% because it's been a year since I've been there.
A&E is the best bet for fashion fabrics, but someone else might be better able to guide your friend. (Suggest Dewey Destin Seafood to eat at and Sexton's seafood to buy fresh shrimp and fish!!!)