I'm helping my 10yr old GD learn to quilt also. I found this book at a LQS Pat Sloan's "I Can't Beleive I'm Sewing"
It has a section on using a sewing machine, buying fabrics, thread and notions, the basics of sewing plus 18 easy to a little more difficult projects. I'm giving it to her for Christmas plus some fat quarters so she can make some of the easy projects quickly as we try to finish her first quilt. Merry Christmas to you and your granddaughter.