I think that a doll quilt might be a good place to start, it's small enough that it will finish quickly and she will have wonderful memories of you making the quilt together. Also a simple 9-patch or even a one-patch lap quilt would be a good project. At that age my Mom was teaching me to sew simple aprons (although people don't use them as much any more, however, I'm sloppy when I cook/bake, so I always have one available), gathered and pleated skirts and in addition, teaching me embroidery. Those are still very special memories to me, especially since she passed away over 40 years ago, but they are a true treasure to me.