Coach, I agree the wrist snap drills are worthless, we don't do them at all. But I will say my DD has seen quite a bit improvement not only in her movement but also in a tighter faster spin, since she has been focusing more on snapping the ball. Now whether it is wrist snap, finger snap or or better whip I can't say, but what she "focuses" on is wrist snap. Her peel is dropping off the table, her curve has a sharper and later break, and her fastball(yes fastball, she pitches a fastball with placement, which for her is exactly like her peel, she is just not over her front leg)is moving better and faster. These are just our observations
I think what you're seeing is the result of a sharp release, versus a long, lazy release that many girls have. I always like to explain that it's called a release point, not a release line, so you should try to make it happen over as short a distance as possible. Sounds like that is what your daughter is achieving, which is great.
Using that snapping a towel example again, if you use a slow, wide movement you can't make the towel snap. But if you make it a short, quick movement, ouch! At the same time, there's no muscle in the towel. The end, which corresponds to the hand and wrist, is quick and loose, and that's what allows it to transfer the power from you down the length of the towel.