You didn't say how old your granddaughter is, because if she were 4-5 I would start with the old fashion sewing cards. When I was 8 years old, my best friend had one of those Singer for kids machine. It was red and I thought it was the best thing ever. However, my mom said if I was going to learn to sew I needed to use a real sewing machine. She taught me on her Singer 15-91. It is in a cabinet - with a knee control. (I have that machine now.) I loved sewing then and now. But I did start off with the cards when i was 4 or 5, then I learned to embroider and made kitchen towels and pillow cases. I do not remember my mom ever sitting and embroidering - but she felt I needed to learn basics before using her machine when I was 8. I even made doll clothes by hand with scraps.
My best friend's mom must have had a fancier machine because Judy was not allowed to touch it. And her mom had lots of wonderful fancy scraps of fabric and lace. We had so much fun.