You can make your own flip flops for her if you can't find any at a store. I used to make my own, and it would be a great little craft project that y'all can do together.
One thing I used to do - Buy some bandanas (they have a bunch of different ones at Hobby Lobby) and cut them into strips and tie them in knots around the straps of the flip flops. I even used to add little Christmas bells tied to ribbons in there, and that was always fun. You can add flowers w/ a hot glue gun.
If you do go to Hobby Lobby, usually they have fliers with different kinds of craft ideas. If you look, they should have somefliers w/ different ideas for flip flops.