Aspie thinking:
"We always have a bath in the evening.
Oh no, a bath in the morning.
Heck, a bath in the morning.
Double heck, a bath in the morning!!!!
Oh my, what can it mean? If the bath is now, what happens next? End of World Alert - there are no baths in the morning, that doesn't happen, the world is indeed ending. All I know about the world has now collapsed!
Aha, pyjamas and no scratchy new clothes? OK...can just about cope with bath in morning if there's pyjamas to look forward to. It'll be ok if there's pyjamas and bed next. That's expected...
Oh no, it's not pyjamas. It's scratchy clothing.
'Out of Spoons' Error! Error alert! World has gone completely mad! Unable to compute what will happen next! Clothes hurting - sensory overload/world-gone-mad overload!! Arrghhh!!! Sister talking to me - no computing room left for conversation - can't understand the words, don't know what to say, Error! Error! Oh no, Mum...eye contact, arrghhhh -that hurts too, make it stop, why won't you make it stop, it HURTS! "
How to explain that to a 3 yr old? I'd do it as a craft game. I'd make 'spectacles' out of two short cardboard tubes so she can see how little we can focus on, and get her to feel sandpaper/emery board to see how scratchy the clothes are, and cover her ears to explain how it is not to be able to 'hear' people properly when we're stressed, and explain that this is what the world is like for her brother and sometimes he gets scared and angry if things are different. But that he might find hugs to be scratchy too, etc, so you'll have to find out what helps him. And that it's not her fault and it's not up to her to make it better, but it's really kind of her to care.