N.S.
I had to LOL a little because we just went through this with my 9-year old SD. She's 9 going on 16 with an attitude to match!
First we cut out all the TV, video games, cell phone, iPod etc. We cut out the sugar.
We sat down and discussed her responsibilities, chores, the way she treated family members, etc. We let her know EXACTLY what was acceptable and what was not. We let her know that she has a responsibility as a member of the family. We let her know our responsibilities.
Then we had "attitude adjustment day." She woke up when daddy got up for work (early on a weekend!) and she began by cleaning her room. She was to work all day long until her attitude adjusted itself. I know there are people out there who don't think that chores should be given as punishment, but we phrased it as WE couldn't get OUR work done because we have to stand over her or constantly remind her to do things. So now she was going to do our work. I had her doing all sorts of chores, but I didn't yell or make her feel bad and I praised her for everything she did.
At 9:00am she was grumbling.
At 10:00am she stopped grumbling and was actually working.
By noon she was cleaning out the pantry and SINGING.
By 1:00 she was vacuuming and DANCING while doing it.
At 2:00 I said she was done and she asked for MORE CHORES!!!!
My SD was so proud of all the things she did. She opens the pantry and smiles because it's all nice and organized and SHE did it! We continue to point out how nice things look because she helped.
We do have a changed attitude. No, she's not perfect but she treats us much better now. She does her chores without getting mad or refusing to do them.
We have to do the Attitude Adjustment Day about once every six months. It has always worked. I think it helps her to feel needed, it helps her to see that when she does things it makes a difference, and nothing makes you enjoy your playtime more than work! The key for Attitude Adjustment Day is you do have to fill it with praise for your daughter for everything she does. Reinforce the good behavior and ignore the grumbling. They WILL grumble at first but it always goes away.
Good Luck!