I used much the same method as for the snap-happy bags I've made in the past (book bags).
I thought the snappy closure would make it quick and easy to get in to, and I included a layer of plastic on the outside of the bag and added handles so that she could carry it over her shoulder easily.
Lastly, I added her (very long) name to the front just to make it special!
Mackenzie was absolutely delighted with it....
and I know it made my husbands day to be able to give her something special.