That's really the key. "life threatening assault". Tasers aren't designed or meant to be disciplinary tools or punitive tools. They're to disable and neutralize a threat. What on earth kinda threat could this girl have posed that would have justified the use of the taser?

Maybe some other facts of the case will come to life? She had a weapon? In the heat of the moment I could see reason behind using it then. But it just doesn't seem that was the case in this situation.

Sounds to me like the officer just got lazy and negligent.