A Different Version?

I know I have seen a movie titled "The Bad Seed or A Bad Seed, but it does not have these characters in it. It is about an adopted brother and sister which go to a foster home. The girl (Catherine) is very violent and hurts her brother, the dog (stabbing it with a pin or something like that) and a few others. I can't find anything about this movie anywhere on the web and am SOOOO frustrated. There was a soical worker with shoulder-length auburn hair, that inflicts extreme therapy on Cat. They come to realize that Cat was physically and sexually abused by her father at a young age. One of the quotes from the little girl during a memory is "Bad Cat, Bad Cat." Does this ring any bells with anyone? Can anyone tell me who any of the actors are?