There is such a craze to learn all four movement pitches as early in a pitcher’s training life as possible. That is leading to a lot of pitchers with four average pitches instead of pitchers with some great stuff.
It is better to have one or two great pitches, than four average pitches.
At the college level movement and location are very important. Pitchers need superior command of a pitch rather than average command of multiple pitches. When we say superior command, we are talking about being able to hit locations that are different only by a few inches, and being able to do that any time. Having one go-to pitch that works every time is significantly more effective that any number of “ok” pitches.
At the college level vertical movement pitches typically are more dominant than horizontal movement pitches. If you look at the sweet spot on the bat lengthwise and width wise, the sweet spot lengthwise is a lot bigger than width wise. So your curve and screw balls have to move a lot more than your drop or rise balls to have a batter miss hit them.
Changing speeds without the batter being able to see that change is also very effective.
Focus on great command of one pitch and then move on to learning a second one.
Experiment with different phrases and ask the player what she feels as you work to coach good timing and decision-making in a swing.