Is this an illegal pitch

[paulg68]

We have a pitcher that starts with pivot foot on the rubber and non pivot foot touching the rear of the rubber within the width of the rubber( perfectly legal). When she pitches she lands with here non pivot foot outside the rubbers width when delivering the pitch. Most times the heal would land withing the rubber width but sometimes it is outside the rubber completely. She is basically stepping across here body to through a curve that starts at a right hand batter and breaks away. We really don't find anything in the book about the non pivot foot landing outside on delivery as being illegal unless it starts outside at the stance.

This is NFHS rules HS varsity softball