Oh my goodness Thornrose! You could be describing me and my own 8yo dd1 - exactly! (except the Aspergers.)
I can find no real pattern to what triggers dd1's outbursts. I shall be watching this post eagerly for good tips because for me, things are getting to the point that I dare not take her out some days! It is also getting in the way of my relationship with her now. The cumulative effect of her bad behavior over the years is weighing me down and the older she gets, the more devastating and embarrassing I find her behavior.
My dd1 is a true Jeckyll and Hyde! She is an angel, on the whole. She is impeccably polite and well spoken, helpful, attentative, thoughtfull, ... People often comment on how wonderful she is. But, every now and then (about twice a month) she will become a horrible, vile, violent, spitting, hitting, swearing, hateful, angry, monster! There seems to be no real rhyme or reason for these sudden outbursts, sometimes she will wake up in a foul temper and explode over wonky tights or itchy clothes or some such trivial thing, other times she will wake up in a foul temper but is okay. When she explodes, anything I do or say is like food to her flames - its like she eats the chaos she creates, and with relish!
I have noticed that she is more likely to be awful when she hasn't slept well (she is not a great sleeper, and is often up and about by 6am), when she is hungry, when she is poorly and when she needs the loo. I have also noticed that when I am feeling tired and grumpy she is more likely to blow-up, I don't know if this is because I am not as good with her and so she becomes annoyed with my manner, or if it is because I am slower at spotting/reacting to her triggers. But I can't spend my life pandering to her whims, there has to be a point that she can spot her own triggers, before they trigger anything - surely she should notice that she is hungry or thirsty, or tired or feels poorly (she will never say when she feels ill - I have to deduce it from all the other 'possible triggers'). And surely there must be a point at which she is able to positively adapt her behavior when people around her are grumpy or are having a bad day!