I agree that's one common cause. Another is striding to the glove side of the power line, which also tends to close the shoulders prematurely. Then there is pulling the ball behind the head at the top of the circle. That will offset the circle and cause it to align toward the inside. Those are a few things to check.Doc,
Often, when I see this problem it is the glove hand that is the cause. The pitcher will be swimming the glove out to the side and causing the shoulders to turn breaking the ryhtum and timing of the windmill and release point. ,
Might want to check and see if your pitcher is doing that as the cause of the problem.
For little i've seen before,when ball goes too low and inside often problem is in locked elbow at the top of the circle.If all mech is good but ball go in the dirt,let her know to relax a little her elbow.And let her establish mental time and routine to go back to the mound after every pitch very easy,cause this will affect her body reaction and will keep out hitters from timing her pitches.Marc, I have a young girl, 10,who about every third pitch, throws the ball deep inside on the right side and in the dirt. She is right-handed and has really good mechanics and control except this problem. She does not lean enough to make this bad of a pitch. Is it mental or a grip problem?