Drugs....
One question.. is she very physically active.. such as playing outside...games etc etc..?
One thing we have noticed is that our 6 year old boy can get really ratty and 'willful' if he isn't 'run' every day for a while.. a bit like a dog...
Once he has been out for a 'walk'... and he has had a good run and play outside he really is in a better mood and far 'happier'...much more agreeable and a joy to have around.
SO we get him out and about every day.. works wonders... we even have him repsonding to the whistle..