Whatever you decide to do, you need to pick a method and go with it. What's the point of paying a coach to teach you something if you are going to practice another way.
There is some information in this thread concerning the roll-over and the peel drop. Pay close attention to the posts from Sluggers. His daughter was an accomplished collegiate pitcher and apparently the drop was her bread and butter pitch.
If she has her whip/IR down, put a stripe on the ball and see if she can get 12/6 spin. If she does=drop ball. If she tends to get more of a spiral spin, ask her to see if she can change the orientation of the spin(stripe) on her own. If she struggles with that, then she can start trying the various cues to find one that works for her.
Whatever you decide to do, you need to pick a method and go with it. What's the point of paying a coach to teach you something if you are going to practice another way.
I agree with canyonjoe. Our situation was a bit different than most. DD's first pitching coach tried and tried to get her to point the elbow, but eventually realized that what DD was doing was working for her. She stopped tinkering and allowed her to use what came naturally. I'm guessing that we were lucky in this sense. I'm not sure how many coaches would have allowed a student to do that.