I'll be honest with you, unless a still photo is taken at a moment when the pitcher has both feet in the air and you can SEE air between her feet and the ground, there's no way to know how the pitch in its entirety turns out. That's my opinion. You need a video instead. Unless a still photo catches the moment when the foot is pushing off a second time in front of the pitching plate and the ball is still in her hand you can't say for sure she's wrong. Again, you need a video.
In my opinion; most pitching instructors will not teach a motion or mechanics that result in an illegal pitch. It has been my experience that the girls lose sight of what they are taught, unaware of the consequences. It is reasonably common to have a pitcher get her timing of the upper torso out of whack with the lower torso. She'll step out too soon after initiating her pitch and her arm spin is late, resulting in a late release or after her footwork is complete. Kids find ways to get back on track and some teach themselves to hang in the air while they get the arm back around or they'll instinctively put the pivot foot back down and push off again. After all; they know what supposed to happen upon release so they are trying to get to that position in the mechanics of the pitch. I honestly believe this to be a common mistake and until an instructor explains things to them they'll continue to throw incorrectly. In my winter sessions indoors, I use a mirror and have the girls throw socks while watching themselves. Many times within 20 throws, we can fix the timing issue and continue with our lesson.
Again, I don’t believe it’s taught. Also, I don't believe the girls are aware they do it most of the time.
There's still a proper way to do things and kids are human beings. They'll make mistakes. Mistakes are a part of the game. This timing issue is something for everyone to consider when you analyze a pitcher's form. It can be corrected and with all the elements of the pitch that a kid is trying to remember, I think it's easy to see how they can get out of sync once in a while, especially when they are in a game and changing from pitch to pitch.