I had a hard time following this, so I might not have understood everything you are saying here. However, I will tell you that 11 year olds can be just awful. I think your 11 year old hit that particular Twilight Zone and only your diligence and time can help.
Take her bed away from her. Put her mattress in the floor. Every single thing that she uses to hurt her sister or fight with you over, goes away. Don't bother to argue with her about it. Tell her once, and then just remove it. It's fine if she "doesn't care". You have given her a consequence, and she will continue to have consequences if she doesn't behave. When she has lost everything in her room, computer privileges and the camera, she will finally start thinking about how she talks to her sister and how she acts.
When she is taking a break from being Broomhilda, compliment her for what she does well. Try hard to find at least 3 compliments a day. At least once a week, take her out somewhere by herself - just Mom and daughter. She needs one-on-one time with you, even if she doesn't want it (or even if you don't want it right now.) DON'T yell for her to knock something off. Get up and go to her and tell her to stop - no saying that you'll knock her block off (sorry if I'm not understanding Broomhilda and the knock her block off thing.) The point is, that she will start talking like that if you do it to her.
If you keep working on this, without losing your temper, without giving up, without acting like you are losing control, it will get better.
And again, get rid of her bed. For Heaven's sake. No one said a kid has to have anything to sleep on except a mattress. Big statement here, Mom.
Good luck,
Dawn