How tall is her Mom, and what is her shoe size? These give a sort of decent idea of what to use for a length of pull compromise. When I built my daughters gun I settled in a 12 inch pull. Guessing her teen age and potentially adult size. It was just a bit long the first year, the next, and now, almost twenty yeas later perfect. It was built when She was eleven. Her sons are using it now. Now I need to build a left handler for my granddaughter who is right handed and left eye dominant. I got lucky mom was petite, daughter looked to be, and turned out to be. BJH