Pitching is very demanding and requires lots of practice and dedication. It is not only very harsh on an individual's time schedule, but on her body as well. I have seen so many pitchers "blow out" their elbow or their shoulder and have to stop pitching. That is why my method of learning to pitch focuses on using the legs just as much (if not more) than the arm. This lets the arm be used merely as a tool to get the ball to its target. This method also gives the pitcher a better chance at a long career in fastpitch.
When I work with beginners, I go step-by-step, breaking down the wind-up into tiny parts that can be practiced in pieces before putting it all together. I am a fundamentals "nut" and believe that you can not create a great pitcher without making sure she has all the basics down first. You don't build a house on bad foundation, right? The same priniciple applies here. I have a hard time believing that a pitcher should try to learn different types of pitches before she can consistently throw strikes, even if her coach is pressuring her into learning these new pitches. That is a losing situation all around.