?

I have a little sister that is seven, and she still acts like she is three. she doesn't listen, acts out, and is extremely immature compared to other seven year olds. I have tried to talk to my parents about it but all the say is "She doesn't know any better, She is only seven." But to me, seven is old enough to know right from wrong. What should I do? And is her behavior normal?

I did a drama at kentucky church of God youth camp around 2001-2004 and it had something to do with chains and breaking free or being set free or something and I can't remember the name of the song or anything. If anyone was there and knows what I am talking about or you think you may know the song I'm trying to think of please let me know. Its driving me crazy!