The incident with the girl and her brother

I spoke to my younger daughter today about the incident at her house between the girl and her 7 year old brother that such an uproar. Both my older daughter and her friend, both of whom are referred to as "auntie", are adament that the girl should be committed for this incident and will not let it go. I have not stopped hearing about it from my older daughter over the last 3 weeks, and last night, she told the girl that she was not to be trusted with the one year old girl that is my older daughter's daughter.
Apparently, by the time the girl reached my younger daughter's (her mother's) house, she was exhausted and in a bad mood. She was not made to feel welcome, and the 7 year old was bugging her and her mother was bragging about his accomplishments in school, which pushed a few important buttons for the girl, as this is a small part of what she never got from her mother.
To get the 7 year old to leave her alone, the girl punched him in the stomach. So, her mother sent the boys (there is also a 5 year old in the household) upstairs to play, and the girl, shortly thereafter, decided to go take a nap. When she tried to pass the boys in the hallway upstairs to get to the bedroom, the 7 year old tried to kick her and she grabbed his ankle and he went flying into the furniture.
For this, both aunties decided that the police should be called and the girl should be institutionalized because her issues were apparently not being dealt with by me adequately. My older daughter has grabbed onto this theory like a dog with a bone, and imagined herself the injured party, as well, and has told the girl that she cannot trust the girl around her baby.
This is the same daughter that constantly accuses me of overreacting.
Wow.