She's discovered the power of no. She has it, and you want her to have it really - you want her no to have power because there will be times in her life when she needs to use it. Many, many times, and she needs to be able to without it being painful or making her feel guilty or ashamed. That's how it was explained to me anyway, and it took me a while to understand what they meant, but I am glad I did, as I'm glad that 8 year old of mine (now a teenager) is happily saying no to a lot!
Agree that rewards speak much more than punishments, so it helps to make sure they overwhelm the bad bits. Ideally, rewards should be instantaneous and lasting, and punishments are best thought out and served in the cold light of 'what am I trying to achieve from this' and more in the form of teaching a new life skill. I'd dye some pasta red and add ONE for bad behaviour not dealt with (where there isn't an obvious way to deal with it). Then, on a good happy day for all, count up the pasta and decide what to do about the red ones.
Perhaps beforehand you could (together) make helpful tokens, such as making bed, pairing socks, tidying shoes, tidying games and toys, making a drink for someone, playing a game with someone, wiping table and counters, cleaning sink, tidying tupperware, wiping skirting boards, feeding & cleaning out pets, washing bath, making sandwiches/toast, letting someone else choose the TV programme, etc. Whatever kind and loving behaviour she is ready for, and she could pick one token to do for each red piece of pasta in her jar, and share them between other members of the family, for them to call in as favours when it suits them. (It could be argued that in all fairness, you should have a pasta jar as well and do the same, but with Mummy sized tasks!
)