We are attempting to bring new adult female into family... We have two adults now. After her vet clearance I brought the new gal into cellar.. She was once someone's kitty. She settled in nicely, SO FAR. Our other two knew she was down there.. Our female growled like a dog for a couple hours. The male wasn't sure what to think.. Now the 9 lb gal is attacking her 20 lb brother like he is a stranger... ANY ideas what could be going on????