The first thing I always look at is the lower body and how it's connected to the girl's mechanics. Whether you love absolute velocity or spin rate, arm speed crucial to generate both. You can't generate arm speed at release if your lower body is not being used. Unfortunately, I see a lot of kids who are 6'0" and taller who appear the have been coached to simply step and throw. A sad waste of the genetics that have provided them the potential to have elite arm speed.