DiamondDad
If your DD is like most pitchers, she already has three different speeds. The drop should be her fastest pitch, the curve is probably 3-4 mph slower then the drop, and the change up is probably 10-12 mph slower then the drop. I'd say this is a good start on variation of speeds, plus each of these pitches is thrown at a different release angle/variation of movement so it creates another dimension for the hitter to deal with. IMO, an accomplished pitcher should have four distinctively different speeds and that they are created because of four different movements on the ball (which in turn means four different amounts of finger surface behind, under, or on the side of the ball putting varying amounts of energy into the ball).
As your DD becomes more accomplished and has added top end speed (which gives her some space to create some separation of speeds) she can work on an offspeed pitch......this could be an offspeed drop, offspeed curve, offspeed rise, etc. then she should have four distinctively different speeds and movements. Life barely gets any better then this.....
