Ratbag, you shouldnt take offence at the comments in here. They werent directed at you or your family...and lets be honest, having a mental disability isnt always an excuse.
Before you get too upset about that, my sister has Aspergers (among other things) and while she is high functioning (she lives by herself, and actually has a baby - god we all panicked about that - but she has surprised us in in a big big way...though that can change in a second) she can be very hard and very frustrating to deal with and a number of us have been physically assaulted by her and had the police on her at times, so I am not just saying the above to be an asshole. I have experience with this kind of stuff.
I have to admit, I LOLed about her taking the rubbish out without a top on. Probably a bit mean but I found it funny nontheless.
In regards to actions, I would have spoken directly to her and if she does it again then id be going to the parents. I am lucky though, my OH is a bit of a nutjob (not actually nutty, but I can never think of the right word) so I dont really have to worry about anyone turning up at our house and threatening us coz if they did, theyd be biting off more than they can chew (and not just from my other half).