I agree with the others that first ask her mom and dad to make sure they are in agreement.
If her mother doesn't sew it may be best to wait a couple years. Or do you live close by? I ask because if something goes awry with the machine it can be very scary for her and mom will have no idea what to do. I was 8 when my mother taught me to use her machine, she was a stay at home mom, so she was there when I sewed. There are so many things for her to sew by hand now, and perfecting a good stitch is a valid skill, since it sounds like she enjoys hand sewing. I was sewing doll clothes and also learned embroidery. When I was in Jr. High (13) I took home-ec. I did a lot more machine sewing after that.