Ooooooooooor people just shouldn't keep nasty, territorial, dangerous animals as pets and expect that their wild nature will be tamed. Just a thought.

Ooooooor you can use your brain and not be so quick to blame the bird- the bird is probably frightened and on edge right now. Parrots are intelligent and can be tamed, and make wonderful pets once they are trained. Same as a dog or any other animal. You just have to do some research and learn how to properly introduce a new bird to your house.

When did I blame the bird for anything? I merely stated that it is nasty, territorial, and dangerous. You can also train a tiger. Does that make it a good pet? "commenters should keep their filthy mouths shut." Sounds like the bird isn't the only nasty thing around here...

I'm just wondering why it wasn't in a cage. Why was a huge-ass new bird given the run of the place?

Birds can just be mean sometimes, and if it is a new bird, OP does need to let him/her get used to it's home, I have 2 birds who I love, but they sure can frustrate me sometimes! And it hurts like hell when they bite!!!

Exactly...if given a cage, that cage becomes its home and it will be less territorial of the area outside. No cage ---> the whole house becomes the parrot's property and you're more likely to be attacked because you're on the parrot's turf :) but then your sister has to be careful going in its cage. My bird gets very upset when I have to go in his cage because he feels his space is invaded, so I make sure he's out of the cage playing beforehand. He loves his cage and goes in there by himself when he wants to feel safe. Oh...another thing OP can do is cover part of the cage or put it in a corner so the bird feels more protected. I wonder what type of bird the OP's sister has. I have a cockatiel - small but very temperamental species.