Pitcher Stepping Back Before Pitch (NFHS)

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Using NFHS rules for Fast-Pitch Softball.

I have a questions about a pitcher taking a step backward before stepping forward to deliver the pitch.

I will do my best to describe what she is doing.

-With pivot foot on the rubber and non-pivot foot either toeing the back of the rubber or slightly behind the rubber, hands down by her side; ball in hand.
-Prior to the pitch, she will take a small step backward with her non-pivot foot while bringing her hands together.
-Once hands are together, she will begin her step forward with her non-pivot foot and start her delivery.

Have one coach that complains about it every game claiming that it is wrong and that you can't take a step backward. Claims to have sent a video to several pitching coaches that she knows in SoCal and Kansas (I think) and they all agree that it is illegal.

As I understand the rule below, it is a legal pitch.
NFHS 6-1-2b states "Any step backward shall begin before the
hands come together. The step backward may end before or after the hands
come together."

She steps backward as she is bring her hands together.

Am I right or wrong?