She takes things to heart and when her sister makes off hand comments...D11 takes them and buries them deep. I need to address this with her. She needs an extra strong sense of self to fend that criticism off and D20 needs to shut the he!! up.
You don't think they could be two sides of the same coin? Your d 20 doesn't sound like a happy bunny either, and this is her way of expressing it. My dil and her sister are very different. The mother is very like her other d, and as a result my dil felt excluded, but really, it is like the reversed out negative.
The children in a family where one has special needs may act up because they can feel excluded - from the sympathy, the attention, the special bond, whatever.
I am not excusing your elder daughter, she needs to grow up, nor am I criticising you, just saying that the behaviour of every family member usually relates to the others.
As you become stronger i think you will change the dynamic
