I started using a weighted ball when I was in high school for wrist snaps and the "3 oclock" drills only. In college my new pitching coach had me throw full distance/speed with a ball 1 oz heavier than regulation. I noticed some significant pain in my shoulder after using the heavier ball. Whatever you decide to do, and it is your decision, make sure that your DD will tell you if she starts to experience any pain or discomfort, it could lead to bad things.