Oh I wish I had read this thread sooner - am too tired now to read it all properly, I have just skimmed it - so sorry if I'm repeating/being irrelevant.
Emkana, your dd2 sounds so much like my dd2 (and she has a younger brother too!). Only she is 8.5! Her behaviour is so much better than it was, but she is still hard work and I suspect always will be. Dh and I were talking about her this lunchtime, and I said that it's as if she doesn't have "brakes" - she is seemingly unable to make herself stop and think, "hold on, this isn't such a good idea, if I do this I will get punished" - despite the fact that she is punished, every time without fail!! She gets into trouble a lot at school, mainly for impetuous silly behaviour.
All this sounds very negative, but it's not meant to be. After a lot of anguish and soul-searching dh and I had to learn to let her be herself within limits, and not place such high expectations on her (dd1 in comparison, is an absolute angel - so we try not to compare!!). She has a generous and loving nature and we try to concentrate on that.
The other thing we find is that, whatever she has that she enjoys, she will always want more - sweets, attention etc (again, back to the "no brakes" thing). So whilst some individual attention is good, it was never the answer for us because she would always act up when she had it (over-excitement I think). She is much better at handling it now, but still "overdoes" it when getting one-to-one. She wouldn't miss out on one-to-one, but we didn't (and don't) use it as a "behaviour tool" for want of a better phrase.
Playing to her strengths - she loves to help, so we give her little jobs around the house (feeding the dog and taking her for a walk, making meals, vaccuuming etc). She loves wildlife so we encourage her to watch wildlife programmes, go birdwatching, talk about what she knows about deer, snakes etc. All these things have come with time as she has matured, and I'm sure these are things that you will find your dd2 can do as she gets older and can channel her enthusiasm for life in a more productive way.
I hope this makes sense - too knackered to preview. Just wanted to share what a "hard work" child is like once they get older