So, I come to you asking how we can un-learn this habit and re-learn I/R, because there isn't a cue I've read for the lock-it-in drill that is working.
It is such a minor problem for her age, it is not worth worrying about it. It is more important to spend your time working on her arm circle, lower body, accuracy, etc. Like others have said, bullet spin is very common.
I would tell her to extend her arm to the target after release. You were want her arm and hand in the "magician finish".