With all I am learning about pitching, I do not understand why this is called illegal in Women's Fastpitch. About the only advantage the pitcher can gain from this, without the replant, is to be closer to the batter. And only within the circle so not that much. I have proven to my dd that she pitches slower with the leap.
Lines are only used in college, and even then they are useless because the last maybe an inning, usually only a half inning if the pitcher is landing on them alot. I have called a couple of 24" violations, but the pitcher was obviously well outside the width of the pitching plate.
When DD was starting to learn the screw she would push the limits of where the line should be. I think she was called on it once or twice. Once she got her balance and learned the pitch she hasn't had any issues since.
To be honest it wasn't worth arguing. She has size 11 shoes and he whole foot would have to be outside the imaginary lines. She never stepped that far out, but to be honest she shouldn't have been going as far to the side as she was so it was a good reinforcement for her.
I can't recall the last time I have seen a pitcher called for an illegal pitch in the tournaments we have entered. Last weekend we faced a pitcher leaping similar to this girl. We have gotten to the point we don't even bring it to the umpires attention any more.