I need to write this down and get it out of my system so sorry if its long winded!
My 8 year old dd (9 in August). She is moody nearly all the time, she is very selfish and won't do a thing for anyone unless there's something in it for her. She says 'no' to almost everything I ask her to do, unless its something she wants to do obviously! We have endless battles over homework and she doesn't seem to care whether its late in or not. She is doing very well at school but with minimal effort and her teacher has recently been commenting on how slow she is to get any work completed. She says school is boring and she is not really interested in extra curricular activities - in comparison to what her friends seem to do in and out of school. I have encouraged her to try things but she has lost interest very quickly - ie recorder, school choir, drama, computer club. At the moment she goes to Brownies and has said she wants to give that up but I have said absolutely no because I bought the uniform etc. She has also just started swimming lessons which she does seem quite keen on so I am really hoping she keeps up the enthusiasm. 
She is the eldest of 3 - my ds is nearly 6 and my youngest dd is 2.5. My ds is very different to her - enthusiastic, eager to please etc which perhaps exacerbates the challenges we have with eldest dd. I am a SAHM so around all the time for her. She has a very stable home life and I try to make sure they have a healthy diet etc. My dh has a very demanding job and is not around a huge amount during the week so the day to day parenting of the 3 of them is largely down to me.
What I really need help with is disciplining her. I have tried everything but nothing seems to affect her. I have taken toys away (all of them out of her room at one point a la supernanny) but she just said she didn't want them anyway...if we take her pocket money away she says she didn't want to buy anything anyway. If I ban the tv or computer she doesn't seem bothered. What do I have to do to hit a nerve with her??! I have also tried to be positive and give rather than take so have tried star charts where they have to collect a certain number a week to get a prize which is usually around the value of £5. It works brilliantly with ds but dd always wants something worth 3 times that much so can't be bothered! Dh has decided to try getting her to earn her pocket money by being helpful, getting out of bed on time for school etc but shes not having it as she says she can't earn enough to make it worthwhile!
I don't know where to go next with her - can anyone help?