My 13 year old daughter is a brat Help?

First off, she is 13 and it's normal for teens to rebel. That being said, I feel there's something missing to this story. You are asking what to do because she is a 'brat'? Lady, she is a child with rights. You can't ask the online community whether you should let your sister 'beat her a$$'. That is child abuse in most states. If your child is cussing at and pushing little kids down the stairs then you need to seek mental health for her. She should not be 'starved' for storming out. She needs guidance and attention. You said you didn't want her having a Brittney Spears compulsion, yet you told her she couldn't take them outside because they would 'get wet'. There are mixed messages being sent to this girl. She obviously doesn't want to be around the cousins. Why are you forcing her to stay while putting the little ones in danger? This saddens me. I hope you are able to work out the frustrations you and your daughter are experiencing. Soon she may turn to hitting you or worse.