As a Nana myself, I would do the cutting instead. A full-sized quilt for anyone is a huge undertaking, especially a 10 year old's first quilt. She might get frustrated and quit forever. How about a quilt for her dolls? I did that with my granddaughter. I did the cutting and helped her with the sewing. The sewing alone is a big undertaking. Another (safe) option would be to mark the fabric and have her cut with scissors. I've seen too many accidents with rotary cutters in my day!