UPDATE: my 5yo niece is beating up my 8mo daughter...help!
so this just began yesterday, my BIL lives with us due to his recent divorce and he gets his daughter every other weekend. Usually she is such a doll, she always wants to help change the diapers and feed my daughter, and hold her...well, yesterday, my niece, Emma, and I were sitting on my bed with my daughter, Amelia. Amelia starts crawling toward her and my niece pushed her back with force saying, "no, Amelia, don't climb on me!" and I said, "we don't push, Emma, okay? Its not nice and Amelia doesn't know any better" she said "okay" and that was that.
literally 30 minutes later, we are in my living room and Amelia is standing, holding on to the couch, having a good time, laughing and all, and then Emma just comes up and kicks her with full force in the chest and my daughter fell straight back and hit her head on the floor. I'm holding her, trying to console her and I say, "Emma! Why did you do that?!?!". She replied saying, "I wanted to play with her" I told her nobody plays like that, especially not babies, and that she needed to apologize. Emma said "why? She won't understand anyways" and I said, "well then give her a hug and a kiss, she'll understand that." but my niece refused! She said she won't kiss Amelia because she slobbers and she won't hug her. Period.
when my brother in law came home, I addressed the issue and HE GOT MAD AT ME! all he said was "come on Emma, lets go play" and gave me a look like, 'how dare you talk smack about my child'.
later that night, he was outside smoking and Amelia and I were playing on the floor while Emma played a phone game on the couch and she just looks at Amelia and grabs a stuffed animal and chucks it at her! It missed her, so I said nothing. At this point, I feel like there's nothing I can do. I'm not allowed to discipline and I obviously can't address her violence to my BIL and I hardly know her mother, so I'm absolutely stuck.
I told my husband about what had happened and he said, "we just have to really watch Emma around Amelia."
Update: I just tried to talk to BIL about Emma's behavior. Basically this was the conversation:
me: I would like to talk to you about something important and I would appreciate if you just listen, don't interrupt, and don't get mad.
BIL: okay, what is it.
me: there were a few incidences yesterday where Emma hurt Amelia and I think it could have to do with the divorce...
BIL: no it does not! That's your problem! You always have to sit and judge a situation that you know nothing about! The problem is that Emma has always been the youngest in her group of friends and they all play rough zombie games and she is only five! She doesn't understand that Amelia can't play like that!
and then he walked away.