Believe it or not, some children (particularly those who were crack addicted or with FAS) need NO trigger for a tantrum. It could be as simple as ‘she looked at me wrong” to being told to sit down to anything.
This behavior from a six year old is out of proportion and indicates that she is developmentally behind OR she uses this crap at home and it works.
Children who have parents that do not tolerate tantrums do not have this problem UNLESS their child has some other underlying organic problems.
The only time I can remember throwing anything that could be described as a tantrum was in 6th grade, much older than the child in question, so no, I don’t buy that it indicates being developmentally behind. And my parents didn’t tolerate tantrums either. Maybe she’s not trained well, you might be right on that, but since I don’t know her or her parents it’s not my place to say or try to interpret.