There are probably multiple players in the league with ADHD and you don't even know it because it's managed well. I'm a child psychologist, and working with kids with ADHD is something I do regularly. At age 10, assuming the parents have had her properly diagnosed, you shouldn't be seeing such impulsive behavior. The child should be learning self-control skills by this point. We all have our moments, granted, but throwing things as you describe is not acceptable behavior, ADHD or not. Were I the coach, I would sit down with the parents and tell them that I recommend they focus on getting her help with impulse control and anger management and then try softball again. Until she is better able to withhold her own impulses, she could hurt herself or someone else unintentionally. Keep in mind that meds may not solve the problem. Most stimulant medication will be out of her system for afternoon/evening games (although she could have meds in her system for weekend daytime games).