There been numerous instances, arguing and just problematic behavior and attitude from our 10 year old. Last night she went overboard and punched her 9 year old sister several times because the 9 year old faked putting something of our 10 year olds in the trash. The 10 year old hit her knocked her on the ground and then stood over her and hit her like 5-6 times while she was in the ground like a ufc fighter. We have no clue on how to discipline this behavior we have taken things away, we’ve tried grounding. We feel like spanking would not be appropriate. Within the last year her attitude is absolutely terrible, arguing with everyone always has to have the last word on everything, tries being the boss of the other siblings. We are just out things to try please help?