9 is a good age to introduce sewing to a child. I recommend an inexpensive Brother machine, one that has a few "pretty" stitches, as kids have fun trying them out. Mechanical is fine, but the computerized ones usually have more stitches to play with.
Unless your grand daughter is very hard on her things, that should get her through and beyond the initial learning stages. It'll also be light enough to be portable. And if she doesn't take to sewing, than you will have a machine to travel with.